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

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.

Macrophage polarization in pathology

Macrophages are cells of the innate immunity constituting the mononuclear phagocyte system and endowed with remarkable different roles essential for defense mechanisms, development of tissues, and homeostasis. They derive from hematopoietic precursors and since the early steps of fetal life populate peripheral tissues, a process continuing throughout adult life. Although present essentially in every organ/tissue, macrophages are more abundant in the gastro-intestinal tract, liver, spleen, upper airways, and brain. They have phagocytic and bactericidal activity and produce inflammatory cytokines that are important to drive adaptive immune responses. Macrophage functions are settled in response to microenvironmental signals, which drive the acquisition of polarized programs, whose extremes are simplified in the M1 and M2 dichotomy. Functional skewing of monocyte/macrophage polarization occurs in physiological conditions (e.g., ontogenesis and pregnancy), as well as in pathology (allergic and chronic inflammation, tissue repair, infection, and cancer) and is now considered a key determinant of disease development and/or regression. Here, we will review evidence supporting a dynamic skewing of macrophage functions in disease, which may provide a basis for macrophage-centered therapeutic strategies.

Combinatorial and Computational Approaches to Identify Interactions of Macrophage Colony-stimulating Factor (M-CSF) and Its Receptor c-FMS

The molecular interactions between macrophage colony-stimulating factor (M-CSF) and the tyrosine kinase receptor c-FMS play a key role in the immune response, bone metabolism, and the development of some cancers. Because no x-ray structure is available for the human M-CSF · c-FMS complex, the binding epitope for this complex is largely unknown. Our goal was to identify the residues that are essential for binding of the human M-CSF to c-FMS. For this purpose, we used a yeast surface display (YSD) approach. We expressed a combinatorial library of monomeric M-CSF (M-CSFM) single mutants and screened this library to isolate variants with reduced affinity for c-FMS using FACS. Sequencing yielded a number of single M-CSFM variants with mutations both in the direct binding interface and distant from the binding site. In addition, we used computational modeling to map the identified mutations onto the M-CSFM structure and to classify the mutations into three groups as follows: those that significantly decrease protein stability; those that destroy favorable intermolecular interactions; and those that decrease affinity through allosteric effects. To validate the YSD and computational data, M-CSFM and three variants were produced as soluble proteins; their affinity and structure were analyzed; and very good correlations with both YSD data and computational predictions were obtained. By identifying the M-CSFM residues critical for M-CSF · c-FMS interactions, we have laid down the basis for a deeper understanding of the M-CSF · c-FMS signaling mechanism and for the development of target-specific therapeutic agents with the ability to sterically occlude the M-CSF·c-FMS binding interface.

Immunity, inflammation, and cancer: an eternal fight between good and evil

Cancer development and its response to therapy are strongly influenced by innate and adaptive immunity, which either promote or attenuate tumorigenesis and can have opposing effects on therapeutic outcome. Chronic inflammation promotes tumor development, progression, and metastatic dissemination, as well as treatment resistance. However, cancer development and malignant progression are also associated with accumulation of genetic alterations and loss of normal regulatory processes, which cause expression of tumor-specific antigens and tumor-associated antigens (TAAs) that can activate antitumor immune responses. Although signals that trigger acute inflammatory reactions often stimulate dendritic cell maturation and antigen presentation, chronic inflammation can be immunosuppressive. This antagonism between inflammation and immunity also affects the outcome of cancer treatment and needs to be considered when designing new therapeutic approaches.

Unmanipulated native fat exposed to high-energy diet, but not autologous grafted fat by itself, may lead to overexpression of Ki67 and PAI-1

Background

Although its unclear oncological risk, which led to more than 20 years of prohibition of its use, fat grafting to the breast is widely used nowadays even for aesthetic purposes. Thus, we proposed an experimental model in rats to analyze the inflammatory activity, cellular proliferation and levels of Plasminogen Activator Inhibitor (PAI-1) in grafted fat, and in native fat exposed to high-energy diet in order to study the oncological potential of fat tissue.

Methods

Samples of grafted fat of rats on regular-energy diet were compared with paired samples of native fat from the same rat on regular-energy diet and on high-energy diet in a different time. Analysis involved microscopic comparisons using hematoxylin-eosin staining, immunohistochemistry with anti-CD68-labelled macrophages, and gene expression of Ki-67 and PAI-1.

Results

Hematoxylin-eosin staining analyses did not find any atypical cellular infiltration or unusual tissue types in the samples of grafted fat. The inflammatory status, assessed through immunohistochemical identification of CD68-labelled macrophages, was similar among samples of native fat and grafted fat of rat on regular-energy diet and of native fat of rats on high-energy diet. Real-time PCR revealed that high-energy diet, but not fat grafting, leads to proliferative status on adipose tissue (overexpression of ki-67, p = 0.046) and raised its PAI-1 levels, p < 0.001.

Conclusion

While the native adipose tissue overexpressed PAI-1 and KI67 when exposed to high-energy diet, the grafted fat by itself was unable to induce cellular proliferation, chronic inflammatory activity and/or elevation of PAI-1 levels.

Mushroom β-Glucan May Immunomodulate the Tumor-Associated Macrophages in the Lewis Lung Carcinoma

The present study showed that oral mushroom beta-glucan treatment significantly increased IFN-γ mRNA expression but significantly reduced COX-2 mRNA expression within the lung. For LLC tumor model, oral Ganoderma lucidum or Antrodia camphorata polysaccharides treatments significantly reduced TGF-β production in serum. In addition, IL-12 and IFN-γ mRNA expression were significantly increased, but IL-6, IL-10, COX-2, and TGF-β mRNA expression were substantially following oral mushroom polysaccharides treatments. The study highlights the efficacious effect of mushroom polysaccharides for ameliorating the immune suppression in the tumor microenvironment. Increased M1 phenotype of tumor-associated macrophages and attenuated M2 phenotype of tumor-associated macrophages could be achieved by ingesting mushroom polysaccharides.

Phagocytes as Corrupted Policemen in Cancer-Related Inflammation

Inflammation is a key component of the tumor microenvironment. Tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) are prototypic inflammatory cells in cancer-related inflammation. Macrophages provide a first line of resistance against infectious agents but in the ecological niche of cancer behave as corrupted policemen. TAMs promote tumor growth and metastasis by direct interactions with cancer cells, including cancer stem cells, as well as by promoting angiogenesis and tissue remodeling and suppressing effective adaptive immunity. In addition, the efficacy of chemotherapy, radiotherapy, and checkpoint blockade inhibitors is profoundly affected by regulation of TAMs. In particular, TAMs can protect and rescue tumor cells from cytotoxic therapy by orchestrating a misguided tissue repair response. Following extensive preclinical studies, there is now proof of concept that targeting tumor-promoting macrophages by diverse strategies (e.g., Trabectedin, anti-colony-stimulating factor-1 receptor antibodies) can result in antitumor activity in human cancer and further studies are ongoing. Neutrophils have long been overlooked as a minor component of the tumor microenvironment, but there is evidence for an important role of TANs in tumor progression. Targeting phagocytes (TAMs and TANs) as corrupted policemen in cancer may pave the way to innovative therapeutic strategies complementing cytoreductive therapies and immunotherapy.

Exposure of tumor-associated macrophages to apoptotic MCF-7 cells promotes breast cancer growth and metastasis

Tumor-associated macrophages (TAMs) have been found to be associated with the progression and metastasis of breast cancer. To clarify the mechanisms underlying the crosstalk between TAMs and cancer stem cells (CSCs) in breast cancer recurrence and metastasis, we used a co-culture model of macrophages and apoptotic human breast cancer cell line MCF-7 cells to investigate the effects of TAMs on MCF-7 in vitro and in vivo. Macrophages co-cultured with apoptotic MCF-7 had increased tumor growth and metastatic ability in a nude mouse transplantation assay. The macrophages exposed to apoptotic cells also induce an increase in the proportion of CD44⁺/CD24⁻ cancer stem-like cells, as well as their proliferative ability accompanied with an increase in mucin1 (MUC1) expression. During this process, macrophages secreted increased amounts of interleukin 6 (IL-6) leading to increased phosphorylation of signal transducers and activators of transcription 3 (STAT3), which likely explains the increased transcription of STAT3 target genes such as TGF-β1 and HIF-1α. Our results indicate that when cancer cells endure chemotherapy induced apoptosis, macrophages in their microenvironment can then activate cancer stem cells to promote cancer growth and metastasis by secreting IL-6, which activates STAT3 phosphorylation to regulate the transcription of its downstream target genes.

Activating transcription factor 4 promotes angiogenesis of breast cancer through enhanced macrophage recruitment

Angiogenesis plays an important role in the progression of tumor. Besides being regulated by tumor cells per se, tumor angiogenesis is also influenced by stromal cells in tumor microenvironment (TME), for example, tumor associated macrophages (TAMs). Activating transcription factor 4 (ATF4), a member of the ATF/CREB family, has been reported to be related to tumor angiogenesis. In this study, we found that exogenous overexpression of ATF4 in mouse breast cancer cells promotes tumor growth via increasing tumor microvascular density. However, ATF4 overexpression failed to increase the expression level of a series of proangiogenic factors including vascular endothelial growth factor A (VEGFA) in tumor cells in this model. Thus, we further investigated the infiltration of proangiogenic macrophages in tumor tissues and found that ATF4-overexpressing tumors could recruit more macrophages via secretion of macrophage colony stimulating factor (M-CSF). Overall, we concluded that exogenous overexpression of ATF4 in breast cancer cells may facilitate the recruitment of macrophages into tumor tissues and promote tumor angiogenesis and tumor growth indirectly.

Immune evasion in cancer: Mechanistic basis and therapeutic strategies

Cancer immune evasion is a major stumbling block in designing effective anticancer therapeutic strategies. Although considerable progress has been made in understanding how cancers evade destructive immunity, measures to counteract tumor escape have not kept pace. There are a number of factors that contribute to tumor persistence despite having a normal host immune system. Immune editing is one of the key aspects why tumors evade surveillance causing the tumors to lie dormant in patients for years through "equilibrium" and "senescence" before re-emerging. In addition, tumors exploit several immunological processes such as targeting the regulatory T cell function or their secretions, antigen presentation, modifying the production of immune suppressive mediators, tolerance and immune deviation. Besides these, tumor heterogeneity and metastasis also play a critical role in tumor growth. A number of potential targets like promoting Th1, NK cell, γδ T cell responses, inhibiting Treg functionality, induction of IL-12, use of drugs including phytochemicals have been designed to counter tumor progression with much success. Some natural agents and phytochemicals merit further study. For example, use of certain key polysaccharide components from mushrooms and plants have shown to possess therapeutic impact on tumor-imposed genetic instability, anti-growth signaling, replicative immortality, dysregulated metabolism etc. In this review, we will discuss the advances made toward understanding the basis of cancer immune evasion and summarize the efficacy of various therapeutic measures and targets that have been developed or are being investigated to enhance tumor rejection.

Growth and gene expression differ over time in alpha-linolenic acid treated breast cancer cells

SCOPE

Heterogeneity of breast cancer (BC) subtypes makes BC treatment difficult. α-linolenic acid (ALA), rich in flaxseed oil, has been shown to reduce growth and increase apoptosis in several BC cell lines, but the mechanism of action needs further understanding.

METHODS AND RESULTS

Four BC cell lines (MCF-7, BT-474, MDA-MB-231 and MDA-MB-468) were incubated with 75 μM ALA+1 nM 17-β estradiol (E2) or 1 nM E2 only (control) for 24 h. MDA-MB-231 cells were additionally incubated at 6 and 12 h. Viable cell number was measured, and expression of genes related to BC (signaling pathways, cell cycle, apoptosis) was quantified by real-time PCR array. There was a reduction in growth of all ALA treated cell lines after 24 h, and in MDA-MB-231 cells this was time-dependent. Many genes were altered after 24 h, and these differed between cell lines. In MDA-MB-231 cells, several gene expression changes were time-dependent.

CONCLUSIONS

ALA reduces growth of BC cell lines, by modifying signaling pathways, which differ between BC molecular subtypes. The ALA effect on gene expression is dynamic and changes over time, indicating the significance of incubation period in detecting gene changes.

Increased expression of colony stimulating factor-1 is a predictor of poor prognosis in patients with clear-cell renal cell carcinoma

Background

This study aims to evaluate the impact of colony stimulating factor-1 (CSF-1) expression on recurrence and survival of patients with clear-cell renal cell carcinoma (ccRCC) following surgery.

Methods

We retrospectively enrolled 267 patients (195 in the training cohort and 72 in the validation cohort) with ccRCC undergoing nephrectomy at a single institution. Clinicopathologic features, cancer-specific survival (CSS) and recurrence-free survival (RFS) were recorded. CSF-1 levels were assessed by immunohistochemistry in tumor tissues. Kaplan-Meier method was applied to compare survival curves. Cox regression models were used to analyze the impact of prognostic factors on CSS and RFS. Concordance index (C-index) was calculated to assess predictive accuracy.

Results

In both cohorts, CSF-1 expression positively correlated with advanced Fuhrman grade and necrosis. High CSF-1 expression indicated poor survival and early recurrence of ccRCC patients after surgery, especially those with advanced TNM stage disease. Multivariate Cox regression analysis showed CSF-1 expression was an independent unfavorable prognostic factor for recurrence and survival. The predictive accuracy of the University of California Los Angeles Integrated Staging System (UISS) was significantly improved when CSF-1 expression was incorporated.

Conclusions

High CSF-1 expression is a potential adverse prognostic biomarker for recurrence and survival of ccRCC patients after nephrectomy.

High Cholesterol Deteriorates Bone Health: New Insights into Molecular Mechanisms

Many epidemiological studies show a positive connection between cardiovascular diseases and risk of osteoporosis, suggesting a role of hyperlipidemia and/or hypercholesterolemia in regulating osteoporosis. The majority of the studies indicated a correlation between high cholesterol and high LDL-cholesterol level with low bone mineral density, a strong predictor of osteoporosis. Similarly, bone metastasis is a serious complication of cancer for patients. Several epidemiological and basic studies have established that high cholesterol is associated with increased cancer risk. Moreover, osteoporotic bone environment predisposes the cancer cells for metastatic growth in the bone microenvironment. This review focuses on how cholesterol and cholesterol-lowering drugs (statins) regulate the functions of bone residential osteoblast and osteoclast cells to augment or to prevent bone deterioration. Moreover, this study provides an insight into molecular mechanisms of cholesterol-mediated bone deterioration. It also proposes a potential mechanism by which cellular cholesterol boosts cancer-induced bone metastasis.

Modulating the tumor microenvironment with RNA interference as a cancer treatment strategy

The tumor microenvironment is composed of accessory cells and immune cells in addition to extracellular matrix (ECM) components. The stromal compartment interacts with cancer cells in a complex crosstalk to support tumor development. Growth factors and cytokines produced by stromal cells support the growth of tumor cells and promote interaction with the vasculature to enhance tumor progression and invasion. The activation of autocrine and paracrine oncogenic signaling pathways by growth factors, cytokines, and proteases derived from both tumor cells and the stromal compartment is thought to play a major role in assisting tumor cells during metastasis. Consequently, targeting tumor-stroma interactions by RNA interference (RNAi)-based approaches is a promising strategy in the search for novel treatment modalities in human cancer. Recent advances in packaging technology including the use of polymers, peptides, liposomes, and nanoparticles to deliver small interfering RNAs (siRNAs) into target cells may overcome limitations associated with potential RNAi-based therapeutics. Newly developed nonviral gene delivery approaches have shown improved anticancer efficacy suggesting that RNAi-based therapeutics provide novel opportunities to elicit significant gene silencing and induce regression of tumor growth. This chapter summarizes our current understanding of the tumor microenvironment and highlights some potential targets for therapeutic intervention with RNAi-based cancer therapeutics.

HOXB7 promotes malignant progression by activating the TGFβ signaling pathway

Overexpression of HOXB7 in breast cancer cells induces an epithelial-mesenchymal transition and promotes tumor progression and lung metastasis. However, the underlying mechanisms for HOXB7-induced aggressive phenotypes in breast cancer remain largely unknown. Here, we report that phosphorylation of SMAD3 was detected in a higher percentage in primary mammary tumor tissues from double-transgenic MMTV-Hoxb7/Her2 mice than tumors from single-transgenic Her2/neu mice, suggesting activation of TGFβ/SMAD3 signaling by HOXB7 in breast tumor tissues. As predicted, TGFβ2 was high in four MMTV-Hoxb7/Her2 transgenic mouse tumor cell lines and two breast cancer cell lines transfected with HOXB7, whereas TGFβ2 was low in HOXB7-depleted cells. HOXB7 directly bound to and activated the TGFβ2 promoter in luciferase and chromatin immunoprecipitation assays. Increased migration and invasion as a result of HOXB7 overexpression in breast cancer cells were reversed by knockdown of TGFβ2 or pharmacologic inhibition of TGFβ signaling. Furthermore, knockdown of TGFβ2 in HOXB7-overexpressing MDA-MB-231 breast cancer cells dramatically inhibited metastasis to the lung. Interestingly, HOXB7 overexpression also induced tumor-associated macrophage (TAM) recruitment and acquisition of an M2 tumor-promoting phenotype. TGFβ2 mediated HOXB7-induced activation of macrophages, suggesting that TAMs may contribute to HOXB7-promoted tumor metastasis. Providing clinical relevance to these findings, by real-time PCR analysis, there was a strong correlation between HOXB7 and TGFβ2 expression in primary breast carcinomas. Taken together, our results suggest that HOXB7 promotes tumor progression in a cell-autonomous and non-cell-autonomous manner through activation of the TGFβ signaling pathway.

Expression of Sox2 in breast cancer cells promotes the recruitment of M2 macrophages to tumor microenvironment

Transcriptional factor Sox2 promotes tumor metastasis; however its regulatory effect on tumor-associated macrophages (TAMs, M2 phenotype) has not been defined. This study disclosed concomitant expression of TAMs marker-CD163 with SOX2 in human breast cancer and showed that Sox2 in breast cancer cells promotes recruitment of TAMs with altered expression of multiple chemokines, including MIP-1α, ICAM-1 etc. and activation of Stat3 and NF-κB signalings. In addition, TAMs rescued the compromised lung metastasis induced by Sox2 silencing in breast cancer cells. Together, this study documented that Sox2 plays an important role in recruiting TAMs and promotes tumor metastasis in a TAMs dependent manner.

Tumor necrosis factor-alpha-converting enzyme activities and tumor-associated macrophages in breast cancer

The role of the tumor microenvironment especially of tumor-associated macrophages (TAMs) in the progression and metastatic spread of breast cancer is well established. TAMs have primarily a M2 (wound-healing) phenotype with minimal cytotoxic activities. The mechanisms by which tumor cells influence TAMs to display a pro-tumor phenotype are still debated although the key roles of immunomodulatory cytokines released by tumor cells, including colony-stimulating factor 1, tumor necrosis factor (TNF) and soluble TNF receptors 1/2, soluble vascular cell adhesion molecule 1, soluble interleukin 6 receptor and amphiregulin, have been demonstrated. Importantly, these factors are released through ectodomain shedding by the activities of the tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17). The role of TACE activation leading to autocrine effects on tumor progression has been extensively studied. In contrast, limited information is available on the role of tumor cell TACE activities on TAMs in breast cancer. TACE inhibitors, currently in clinical trials, will certainly affect TAMs and subsequently treatment outcomes based on the substrates it releases. Furthermore, whether targeting a subset of the molecules shed by TACE, specifically those leading to TAMs with altered functions and phenotype, holds greater therapeutic promises than past clinical trials of TACE antagonists' remains to be determined. Here, the potential roles of TACE ectodomain shedding in the breast tumor microenvironment are reviewed with a focus on the release of tumor-derived immunomodulatory factors shed by TACE that directs TAM phenotypes and functions.

Macrophages, Neutrophils, and Cancer: A Double Edged Sword

The tumor microenvironment is a well-recognized framework, in which myeloid cells play important roles in cancer development from tumor initiation to metastasis. Immune cells present in the tumor microenvironment can promote or inhibit cancer formation and development. Diversity and plasticity are hallmarks of cells of the monocyte-macrophage lineage. In response to distinct signals the cells of the monocyte-macrophage lineage have the ability to display a wide spectrum of activation states; classical Ml or alternative M2 macrophages represent extremes of a continuum of this activation. Tumor-associated macrophages generally acquire an M2-like phenotype that is relevant for their participation in tumor growth and progression. There is now evidence that also neutrophils can be driven towards distinct phenotypes in response to microenvironmental signals. In fact they can interact with distinct cell populations and produce a wide number of cytokines and effector molecules. Therefore, macrophages and neutrophils are both integrated in the regulation of the innate and adaptive immune responses in various inflammatory situations, including cancer. These findings have triggered efforts to target tumor-associated macrophages and neutrophils. In particular, “reeducation” to activate their antitumor potential or elimination of tumor promoting cells is a new strategy undergoing preclinical and clinical evaluation.

IκB kinase activity drives fetal lung macrophage maturation along a non-M1/M2 paradigm

In preterm infants, exposure to inflammation increases the risk of bronchopulmonary dysplasia, a chronic, developmental lung disease. Although macrophages are the key cells that initiate lung inflammation, less is known about lung macrophage phenotype and maturation. We hypothesized that fetal lung macrophages mature into distinct subpopulations during mouse development, and that activation could influence macrophage maturation. Expression of the fetal macrophage markers CD68, CD86, CD206, Ym1, fibrinogen-like protein 2, and indolamine-2, 3-dioxygenase was developmentally regulated, with each marker having different temporal patterns. Flow cytometry analysis showed macrophages within the fetal lung were less diverse than the distinctly separate subpopulations in newborn and adult lungs. Similar to adult alveolar macrophages, fetal lung macrophages responded to the TLR4 agonist LPS and the alternative activation cytokines IL-4 and IL-13. Using a macrophage-specific constitutively active IκB Kinase transgenic model (IKFM), we demonstrated that macrophage activation increased proinflammatory gene expression and reduced the response of fetal lung macrophages to IL-4 and IL-13. Activation also increased fetal lung macrophage proliferation. Fetal IKFM lungs contained increased percentages of more mature, CD11b(low)F4/80(high) cells that also expressed higher levels of the alternative activation markers CD204 and CD206. Development of fetal lung macrophages into mature alveolar macrophages may therefore include features of both proinflammatory and alternative activation paradigms.

Pharmacological modulation of monocytes and macrophages

Mononuclear phagocytes are major players in diverse pathological conditions which include chronic inflammatory diseases, infection, autoimmunity, atherosclerosis, metabolic disorders, and cancer. Plasticity is a fundamental property of cells of the monocyte-macrophage lineage and a variety of modulators profoundly affect monocytes and macrophages. Tumor-associated macrophages (TAMs) provide a paradigm for macrophage plasticity and anticancer therapeutic modalities (chemotherapy, radiotherapy, and immunotherapy) profoundly affect their function. The development of innovative strategies targeting cells of the monocyte-macrophage lineage may pave the way to innovative therapies for a wide range of diseases.

Tumor-associated macrophages: from mechanisms to therapy

The tumor microenvironment is a complex ecology of cells that evolves with and provides support to tumor cells during the transition to malignancy. Among the innate and adaptive immune cells recruited to the tumor site, macrophages are particularly abundant and are present at all stages of tumor progression. Clinical studies and experimental mouse models indicate that these macrophages generally play a protumoral role. In the primary tumor, macrophages can stimulate angiogenesis and enhance tumor cell invasion, motility, and intravasation. During monocytes and/or metastasis, macrophages prime the premetastatic site and promote tumor cell extravasation, survival, and persistent growth. Macrophages are also immunosuppressive, preventing tumor cell attack by natural killer and T cells during tumor progression and after recovery from chemo- or immunotherapy. Therapeutic success in targeting these protumoral roles in preclinical models and in early clinical trials suggests that macrophages are attractive targets as part of combination therapy in cancer treatment.

Tumor-associated macrophages: from mechanisms to therapy

The tumor microenvironment is a complex ecology of cells that evolves with and provides support to tumor cells during the transition to malignancy. Among the innate and adaptive immune cells recruited to the tumor site, macrophages are particularly abundant and are present at all stages of tumor progression. Clinical studies and experimental mouse models indicate that these macrophages generally play a protumoral role. In the primary tumor, macrophages can stimulate angiogenesis and enhance tumor cell invasion, motility, and intravasation. During monocytes and/or metastasis, macrophages prime the premetastatic site and promote tumor cell extravasation, survival, and persistent growth. Macrophages are also immunosuppressive, preventing tumor cell attack by natural killer and T cells during tumor progression and after recovery from chemo- or immunotherapy. Therapeutic success in targeting these protumoral roles in preclinical models and in early clinical trials suggests that macrophages are attractive targets as part of combination therapy in cancer treatment.

Cytokine networks that mediate epithelial cell-macrophage crosstalk in the mammary gland: implications for development and cancer

Dynamic interactions between the hormone responsive mammary gland epithelium and surrounding stromal macrophage populations are critical for normal development and function of the mammary gland. Macrophages are versatile cells capable of diverse roles in mammary gland development and maintenance of homeostasis, and their function is highly dependent on signals within the local cytokine microenvironment. The mammary epithelium secretes a number of cytokines, including colony stimulating factor 1 (CSF1), transforming growth factor beta 1 (TGFB1), and chemokine ligand 2 (CCL2) that affect the abundance, phenotype and function of macrophages. However, aberrations in these interactions have been found to increase the risk of tumour formation, and utilisation of stromal macrophage support by tumours can increase the invasive and metastatic potential of the cancer. Studies utilising genetically modified mouse models have shed light on the significance of epithelial cell-macrophage crosstalk, and the cytokines that mediate this communication, in mammary gland development and tumourigenesis. This article reviews the current status of our understanding of the roles of epithelial cell-derived cytokines in mammary gland development and cancer, with a focus on the crosstalk between epithelial cells and the local macrophage population.

Dissecting the role of bone marrow stromal cells on bone metastases

Tumor-induced bone disease is a dynamic process that involves interactions with many cell types. Once metastatic cancer cells reach the bone, they are in contact with many different cell types that are present in the cell-rich bone marrow. These cells include the immune cells, myeloid cells, fibroblasts, osteoblasts, osteoclasts, and mesenchymal stem cells. Each of these cell populations can influence the behavior or gene expression of both the tumor cells and the bone microenvironment. Additionally, the tumor itself can alter the behavior of these bone marrow cells which further alters both the microenvironment and the tumor cells. While many groups focus on studying these interactions, much remains unknown. A better understanding of the interactions between the tumor cells and the bone microenvironment will improve our knowledge on how tumors establish in bone and may lead to improvements in diagnosing and treating bone metastases. This review details our current knowledge on the interactions between tumor cells that reside in bone and their microenvironment.

Hematopoietic cytokines as tumor markers in breast malignancies. A multivariate analysis with ROC curve in breast cancer patients

PURPOSE

Plasma levels of selected hematopoietic cytokines: interleukin 3 ( IL-3), stem cell factor (SCF), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF) and macrophage colony-stimulating factor (M-CSF), and the tumor marker carcinoma antigen 15-3 (CA 15-3) in breast cancer (BC) patients were investigated and compared to control groups: benign breast tumor patients and healthy subjects.

MATERIAL/METHODS

Cytokine levels were determined by ELISA, CA 15-3 - using the CMIA method.

RESULTS

A significant differences in the concentration of cytokines (with the exception of IL-3) and CA15-3 between the groups of BC patients, benign breast tumor patients and the healthy controls have been demonstrated. M-CSF has demonstrated higher or equal to CA 15-3 values of diagnostic sensitivity, specificity and the predictive values of positive and negative test results. The M-CSF area under the ROC curve (AUC) was the largest from all the cytokines tested and marginally lower than the AUC of CA 15-3.

CONCLUSION

These findings suggest the usefulness of M-CSF in diagnosing breast cancer, especially when discriminating between cancer and non-carcinoma lesions.

Macrophage colony-stimulating factor augments Tie2-expressing monocyte differentiation, angiogenic function, and recruitment in a mouse model of breast cancer

Reports demonstrate the role of M-CSF (CSF1) in tumor progression in mouse models as well as the prognostic value of macrophage numbers in breast cancer patients. Recently, a subset of CD14+ monocytes expressing the Tie2 receptor, once thought to be predominantly expressed on endothelial cells, has been characterized. We hypothesized that increased levels of CSF1 in breast tumors can regulate differentiation of Tie2- monocytes to a Tie2+ phenotype. We treated CD14+ human monocytes with CSF1 and found a significant increase in CD14+/Tie2+ positivity. To understand if CSF1-induced Tie2 expression on these cells improved their migratory ability, we pre-treated CD14+ monocytes with CSF1 and used Boyden chemotaxis chambers to observe enhanced response to angiopoietin-2 (ANG2), the chemotactic ligand for the Tie2 receptor. We found that CSF1 pre-treatment significantly augmented chemotaxis and that Tie2 receptor upregulation was responsible as siRNA targeting Tie2 receptor abrogated this effect. To understand any augmented angiogenic effect produced by treating these cells with CSF1, we cultured human umbilical vein endothelial cells (HUVECs) with conditioned supernatants from CSF1-pre-treated CD14+ monocytes for a tube formation assay. While supernatants from CSF1-pre-treated TEMs increased HUVEC branching, a neutralizing antibody against the CSF1R abrogated this activity, as did siRNA against the Tie2 receptor. To test our hypothesis in vivo, we treated PyMT tumor-bearing mice with CSF1 and observed an expansion in the TEM population relative to total F4/80+ cells, which resulted in increased angiogenesis. Investigation into the mechanism of Tie2 receptor upregulation on CD14+ monocytes by CSF1 revealed a synergistic contribution from the PI3 kinase and HIF pathways as the PI3 kinase inhibitor LY294002, as well as HIF-1α-deficient macrophages differentiated from the bone marrow of HIF-1αfl/fl/LysMcre mice, diminished CSF1-stimulated Tie2 receptor expression.

Mathematical model of macrophage-facilitated breast cancer cells invasion

Mortality from breast cancer stems from its tendency to invade into surrounding tissues and organs. Experiments have shown that this metastatic process is facilitated by macrophages in a short-ranged chemical signalling loop. Macrophages secrete epidermal growth factor, EGF, and respond to the colony stimulating factor 1, CSF-1. Tumor cells secrete CSF-1 and respond to EGF. In this way, the cells coordinate aggregation and cooperative migration. Here we investigate this process in a model for in vitro interactions using two distinct but related mathematical approaches. In the first, we analyze and simulate a set of partial differential equations to determine conditions for aggregation. In the second, we use a cell-based discrete 3D simulation to follow the fates and motion of individual cells during aggregation. Linear stability analysis of the PDE model reveals that decreasing the chemical secretion, chemotaxis coefficients or density of cells or increasing the chemical degradation in the model could eliminate the spontaneous aggregation of cells. Simulations with the discrete model show that the ratio between tumor cells and macrophages in aggregates increases when the EGF secretion parameter is increased. The results also show how CSF-1/CSF-1R autocrine signalling in tumor cells affects the ratio between the two cell types. Comparing the continuum results with simulations of a discrete cell-based model, we find good qualitative agreement.

NCOA1 Directly Targets M-CSF1 Expression to Promote Breast Cancer Metastasis

In breast cancer, overexpression of the nuclear coactivator NCOA1 (SRC-1) is associated with disease recurrence and resistance to endocrine therapy. To examine the impact of NCOA1 overexpression on morphogenesis and carcinogenesis in the mammary gland (MG), we generated MMTV-hNCOA1 transgenic [Tg(NCOA1)] mice. In the context of two distinct transgenic models of breast cancer, NCOA1 overexpression did not affect the morphology or tumor-forming capability of MG epithelial cells. However, NCOA1 overexpression increased the number of circulating breast cancer cells and the efficiency of lung metastasis. Mechanistic investigations showed that NCOA1 and c-Fos were recruited to a functional AP-1 site in the macrophage attractant CSF1 promoter, directly upregulating colony-simulating factor 1 (CSF1) expression to enhance macrophage recruitment and metastasis. Conversely, silencing NCOA1 reduced CSF1 expression and decreased macrophage recruitment and breast cancer cell metastasis. In a cohort of 453 human breast tumors, NCOA1 and CSF1 levels correlated positively with disease recurrence, higher tumor grade, and poor prognosis. Together, our results define an NCOA1/AP-1/CSF1 regulatory axis that promotes breast cancer metastasis, offering a novel therapeutic target for impeding this process.

Colony-stimulating factor 1 potentiates lung cancer bone metastasis

Colony-stimulating factor 1 (CSF1) is essential for osteoclastogenesis that mediates osteolysis in metastatic tumors. Patients with lung cancer have increased CSF1 in serum and high levels are associated with poor survival. Adenocarcinomas metastasize rapidly and many patients suffer from bone metastasis. Lung cancer stem-like cells sustain tumor growth and potentiate metastasis. The purpose of this study was to determine the role of CSF1 in lung cancer bone metastasis and whether inhibition of CSF1 ameliorates the disease. Human lung adenocarcinoma A549 cells were examined in vitro for CSF1/CSF1R. A549-luc cells were injected intracardiac in NOD/SCID mice and metastasis was assessed. To determine the effect of CSF1 knockdown (KD) in A549 cells on bone metastasis, cells were stably transfected with a retroviral vector containing short-hairpin CSF1 (KD) or empty vector (CT). Results showed that A549 cells express CSF1/CSF1R; CSF1 increased their proliferation and invasion, whereas soluble CSF1R inhibited invasion. Mice injected with A549-luc cells showed osteolytic bone lesions 3.5 weeks after injection and lesions increased over 5 weeks. Tumors recapitulated adenocarcinoma morphology and showed osteoclasts along the tumor/bone interface, trabecular, and cortical bone loss. Analyses of KD cells showed decreased CSF1 protein levels, reduced colony formation in soft agar assay, and decreased fraction of stem-like cells. In CSF1KD mice, the incidence of tumor metastasis was similar to controls, although fewer CSF1KD mice had metastasis in both hind limbs. KD tumors showed reduced CSF1 expression, Ki-67+ cells, and osteoclasts. Importantly, there was a low incidence of large tumors >0.1 mm(2) in CSF1KD mice compared with control mice (10% vs 62.5%). This study established a lung osteolytic bone metastasis model that resembles human disease and suggests that CSF1 is a key determinant of cancer stem cell survival and tumor growth. Results may lead to novel strategies to inhibit CSF1 in lung cancer and improve management of bone metastasis.

Production and characterisation of a monoclonal antibody that recognises the chicken CSF1 receptor and confirms that expression is restricted to macrophage-lineage cells

Macrophages contribute to innate and acquired immunity as well as many aspects of homeostasis and development. Studies of macrophage biology and function in birds have been hampered by a lack of definitive cell surface markers. As in mammals, avian macrophages proliferate and differentiate in response to CSF1 and IL34, acting through the shared receptor, CSF1R. CSF1R mRNA expression in the chicken is restricted to macrophages and their progenitors. To expedite studies of avian macrophage biology, we produced an avian CSF1R-Fc chimeric protein and generated a monoclonal antibody (designated ROS-AV170) against the chicken CSF1R using the chimeric protein as immunogen. Specific binding of ROS-AV170 to CSF1R was confirmed by FACS, ELISA and immunohistochemistry on tissue sections. CSF1 down-regulated cell surface expression of the CSF1R detected with ROS-AV170, but the antibody did not block CSF1 signalling. Expression of CSF1R was detected on the surface of bone marrow progenitors only after culture in the absence of CSF1, and was induced during macrophage differentiation. Constitutive surface expression of CSF1R distinguished monocytes from other myeloid cells, including heterophils and thrombocytes. This antibody will therefore be of considerable utility for the study of chicken macrophage biology.

Platelet-derived growth factor-C (PDGF-C) induces anti-apoptotic effects on macrophages through Akt and Bad phosphorylation

PDGF-C, which is abundant in the malignant breast tumor microenvironment, plays an important role in cell growth and survival. Because tumor-associated macrophages (TAMs) contribute to cancer malignancy, macrophage survival mechanisms are an attractive area of research into controlling tumor progression. In this study, we investigated PDGF-C-mediated signaling pathways involved in anti-apoptotic effects in macrophages. We found that the human malignant breast cancer cell line MDA-MB-231 produced high quantities of PDGF-C, whereas benign MCF-7 cells did not. Recombinant PDGF-C induced PDGF receptor α chain phosphorylation, followed by Akt and Bad phosphorylation in THP-1-derived macrophages. MDA-MB-231 culture supernatants also activated macrophage PDGF-Rα. PDGF-C prevented staurosporine-induced macrophage apoptosis by inhibiting the activation of caspase-3, -7, -8, and -9 and cleavage of poly(ADP-ribose) polymerase. Finally, TAMs isolated from the PDGF-C knockdown murine breast cancer cell line 4T1 and PDGF-C knockdown MDA-MB-231-derived tumor mass showed higher rates of apoptosis than the respective WT controls. Collectively, our results suggest that tumor cell-derived PDGF-C enhances TAM survival, promoting tumor malignancy.

CSF1R inhibition delays cervical and mammary tumor growth in murine models by attenuating the turnover of tumor-associated macrophages and enhancing infiltration by CD8+ T cells

Increased numbers of tumor-infiltrating macrophages correlate with poor disease outcome in patients affected by several types of cancer, including breast and prostate carcinomas. The colony stimulating factor 1 receptor (CSF1R) signaling pathway drives the recruitment of tumor-associated macrophages (TAMs) to the neoplastic microenvironment and promotes the differentiation of TAMs toward a pro-tumorigenic phenotype. Twelve clinical trials are currently evaluating agents that target the CSF1/CSF1R signaling pathway as a treatment against multiple malignancies, including breast carcinoma, leukemia, and glioblastoma. The blockade of CSF1R signaling has been shown to greatly decrease the number of macrophages in a tissue-specific manner. However, additional mechanistic insights are needed in order to understand how macrophages are depleted and the global effects of CSF1R inhibition on other tumor-infiltrating immune cells. Using BLZ945, a highly selective small molecule inhibitor of CSF1R, we show that CSF1R inhibition attenuates the turnover rate of TAMs while increasing the number of CD8⁺ T cells that infiltrate cervical and breast carcinomas. Specifically, we find that BLZ945 decreased the growth of malignant cells in the mouse mammary tumor virus-driven polyomavirus middle T antigen (MMTV-PyMT) model of mammary carcinogenesis. Furthermore, we show that BLZ945 prevents tumor progression in the keratin 14-expressing human papillomavirus type 16 (K14-HPV-16) transgenic model of cervical carcinogenesis. Our results demonstrate that TAMs undergo a constant turnover in a CSF1R-dependent manner, and suggest that continuous inhibition of the CSF1R pathway may be essential to maintain efficacious macrophage depletion as an anticancer therapy.

Molecular changes in bone marrow, tumor and serum after conductive ablation of murine 4T1 breast carcinoma

Thermal ablation of solid tumors using conductive interstitial thermal therapy (CITT) produces coagulative necrosis in the center of ablation. Local changes in homeostasis for surviving tumor and systemic changes in circulation and distant organs must be understood and monitored in order to prevent tumor re-growth and metastasis. The purpose of this study was to use a mouse carcinoma model to evaluate molecular changes in the bone marrow and surviving tumor after CITT treatment by quantification of transcripts associated with cancer progression and hyperthermia, serum cytokines, stress proteins and the marrow/tumor cross-talk regulator stromal-derived factor 1. Analysis of 27 genes and 22 proteins with quantitative PCR, ELISA, immunoblotting and multiplex antibody assays revealed that the gene and protein expression in tissue and serum was significantly different between ablated and control mice. The transcripts of four genes (Cxcl12, Sele, Fgf2, Lifr) were significantly higher in the bone marrow of treated mice. Tumors surviving ablation showed significantly lower levels of the Lifr and Sele transcripts. Similarly, the majority of transcripts measured in tumors decreased with treatment. Surviving tumors also contained lower levels of SDF-1α and HIF-1α proteins whereas HSP27 and HSP70 were higher. Of 16 serum chemokines, IFNγ and GM-CSF levels were lower with treatment. These results indicate that CITT ablation causes molecular changes which may slow cancer cell proliferation. However, inhibition of HSP27 may be necessary to control aggressiveness of surviving cancer stem cells. The changes in bone marrow are suggestive of possible increased recruitment of circulatory cancer cells. Therefore, the possibility of heightened bone metastasis after thermal ablation needs to be further investigated and inhibition strategies developed, if warranted.

Cathepsin C is a tissue-specific regulator of squamous carcinogenesis

Serine and cysteine cathepsin (Cts) proteases are involved in tumor progression. CtsB plays a significant role during mammary carcinogenesis. Ruffell et al. find that squamous carcinomas develop independently of CtsB. CtsC is not required during mammary carcinogenesis but is necessary for squamous carcinogenesis. Dermal/stromal fibroblasts and bone marrow-derived cells express elevated levels of enzymatically active CtsC that regulate the complexity of infiltrating immune cells in neoplastic skin, development of angiogenic vasculature, and squamous cell carcinoma growth. These findings indicate that tissue specificity can define functional significance.

Serine and cysteine cathepsin (Cts) proteases are an important class of intracellular and pericellular enzymes mediating multiple aspects of tumor development. Emblematic of these is CtsB, reported to play functionally significant roles during pancreatic islet and mammary carcinogenesis. CtsC, on the other hand, while up-regulated during pancreatic islet carcinogenesis, lacks functional significance in mediating neoplastic progression in that organ. Given that protein expression and enzymatic activity of both CtsB and CtsC are increased in numerous tumors, we sought to understand how tissue specificity might factor into their functional significance. Thus, whereas others have reported that CtsB regulates metastasis of mammary carcinomas, we found that development of squamous carcinomas occurs independently of CtsB. In contrast to these findings, our studies found no significant role for CtsC during mammary carcinogenesis but revealed squamous carcinogenesis to be functionally dependent on CtsC. In this context, dermal/stromal fibroblasts and bone marrow-derived cells expressed increased levels of enzymatically active CtsC that regulated the complexity of infiltrating immune cells in neoplastic skin, development of angiogenic vasculature, and overt squamous cell carcinoma growth. These studies highlight the important contribution of tissue/microenvironment context to solid tumor development and indicate that tissue specificity defines functional significance for these two members of the cysteine protease family.

Upregulation of glycoprotein nonmetastatic B by colony-stimulating factor-1 and epithelial cell adhesion molecule in hepatocellular carcinoma cells

Considerable effort has been made in elucidating the appropriate biomarkers and the mechanism and functional significance of these biomarkers in hepatocellular carcinoma (HCC). Glycoprotein nonmetastatic B (GPNMB) overexpression occurs in cutaneous melanomas and breast cancer, and it is an attractive candidate for cancer therapy. However, little is known about the expression and regulation of GPNMB in HCC. In this study, we investigated the expression of GPNMB in HCC histochemically and tested the regulation effects of the epithelial cell adhesion molecule (EpCAM) and colony-stimulating factor (CSF-1) on the expression of GPNMB in HCC cells. Our results demonstrated that GPNMB levels were significantly enhanced in HCC compared with adjacent normal liver tissues. In HCC cells, GPNMB expression was regulated by EpCAM and CSF-1 partly through their common downstream product c-myc. Taken together, these results suggest that GPNMB, the expression of which was regulated in HCC cells by the highly coordinated function of various proteins, may be a potential target for HCC therapy.

Tumor associated macrophages and neutrophils in cancer

The tumor microenvironment is a complex framework, in which myeloid cells play important roles in sculpting cancer development from tumor initiation to metastasis. Immune cells are key participants of the tumor microenvironment where they can promote or inhibit cancer formation and development. Plasticity is a widely accepted hallmark of myeloid cells and in particular of the monocyte-macrophage lineage. It includes the ability to display a wide spectrum of activation states in response to distinct signals and classical M1 or alternative M2 macrophages represent a paradigm of this feature. Neutrophils have long been viewed as terminally differentiated effector cells, playing a major role during the acute phase of inflammation and resistance against microbes. Recent evidence questioned this limited point of view, indicating that neutrophils can interact with distinct cell populations and produce a wide number of cytokines and effector molecules. Therefore, macrophages and neutrophils are both integrated in the regulation of the innate and adaptive immune responses in various inflammatory situations, including cancer.

VEGF, M-CSF and CA 15-3 as a new tumor marker panel in breast malignancies: a multivariate analysis with ROC curve

The plasma levels of Vascular endothelial growth factor, macrophage-colony stimulating factor (M-CSF) and CA15-3 in breast cancer patients (BC) were investigated and compared with control groups: benign breast tumor patients and the healthy subjects. Cytokine levels were determined by the use of enzyme-linked immunosorbent assay, CA 15-3 - by chemiluminescent microparticle immunoassay method. Our results have demonstrated significant differences in the concentration of cytokines and CA 15-3 between the groups of BC patients and two control groups. Cytokines have demonstrated equal to CA 15-3 or even higher values of the diagnostic sensitivity (SE), the predictive values of positive and negative test results (PV-PR, PV-NR), and the area under the ROC curve (AUC) in the studied groups. The combined use of tested parameters resulted in the increase of the SE, PV-PR and AUC. These findings suggest the usefulness of both cytokines in the diagnosis of BC, but only M-CSF in discrimination between cancer and non-carcinoma lesions, especially in combination with CA 15-3.

MMP1, MMP9, and COX2 expressions in promonocytes are induced by breast cancer cells and correlate with collagen degradation, transformation-like morphological changes in MCF-10A acini, and tumor aggressiveness

Tumor-associated immune cells often lack immune effector activities, and instead they present protumoral functions. To understand how tumors promote this immunological switch, invasive and noninvasive breast cancer cell (BRC) lines were cocultured with a promonocytic cell line in a Matrigel-based 3D system. We hypothesized that if communication exists between tumor and immune cells, coculturing would result in augmented expression of genes associated with tumor malignancy. Upregulation of proteases MMP1 and MMP9 and inflammatory COX2 genes was found likely in response to soluble factors. Interestingly, changes were more apparent in promonocytes and correlated with the aggressiveness of the BRC line. Increased gene expression was confirmed by collagen degradation assays and immunocytochemistry of prostaglandin 2, a product of COX2 activity. Untransformed MCF-10A cells were then used as a sensor of soluble factors with transformation-like capabilities, finding that acini formed in the presence of supernatants of the highly aggressive BRC/promonocyte cocultures often exhibited total loss of the normal architecture. These data support that tumor cells can modify immune cell gene expression and tumor aggressiveness may importantly reside in this capacity. Modeling interactions in the tumor stroma will allow the identification of genes useful as cancer prognostic markers and therapy targets.

Macrophages stimulate gastric and colorectal cancer invasion through EGFR Y(1086), c-Src, Erk1/2 and Akt phosphorylation and smallGTPase activity

The interactions between cancer cells and their microenvironment are crucial for malignant progression, as they modulate invasion-related activities. Tumor-associated macrophages are generally considered allies in the process of tumor progression in several types of cancer, although their role on gastric and colorectal carcinomas is still poorly understood. In this report, we studied the influence of primary human macrophages on gastric and colorectal cancer cells, considering invasion, motility/migration, proteolysis and activated intracellular signaling pathways. We demonstrated that macrophages stimulate cancer cell invasion, motility and migration, and that these effects depend on matrix metalloproteinase (MMP) activity and on the activation of epidermal growth factor receptor (EGFR) (at the residue Y(1086)), PLC-γ (phospholipase C-gamma) and Gab1 (GRB2-associated binding protein-1), as evidenced by siRNA (small interference RNA) experiments. Epidermal growth factor (EGF)-immunodepletion impaired macrophage-mediated cancer cell invasion and motility, suggesting that EGF is the pro-invasive and pro-motile factor produced by macrophages. Macrophages also induced gastric and colorectal cancer cell phosphorylation of Akt, c-Src and ERK1/2, and led to an increase of RhoA and Cdc42 activity. Interestingly, whereas macrophage-mediated cancer cell c-Src and ERK1/2 phosphorylation occurred downstream EGFR activation, Akt phosphorylation seems to be a parallel event, taking place in an EGFR-independent manner. The involvement of EGF, EGFR-downstream signaling partners and MMPs in macrophage-mediated invasion provides novel insights into the molecular crosstalk established between cancer cells and macrophages, opening new perspectives for the design of new and more efficient therapeutic strategies to counteract cancer cell invasion.

Seed, soil, and beyond: The basic biology of brain metastasis

First invoked by Paget, the seed and soil hypothesis suggests that the successful growth of metastatic cells depends on the interactions and properties of cancer cells (seeds) and their potential target organs (soil). In the context of the seed and soil hypothesis this review examines recent advances in the understanding of molecular and cellular features that permit transformed epithelial cells to gain access to the blood stream (intravasation), survive their journey through the blood stream, and ultimately traverse through the microvasculature of target organs (extravsation) to deposit, survive, and grow in a foreign tissue environment. In addition to a review of the clinical and experimental evidence supporting the seed and soil theory to cancer metastasis, additional concepts highlighted include: (i) The role of cancer stem-like cells as putative cells of metastatic origin (the "seeds"); (ii) the mechanism of epithelial to mesenchymal transition (EMT) in driving epithelial cell conthose molecules do no blood stream to avoid anoikis, or anchorage independent cell death; and (iv) the reverse process of EMT, or mesenchymal to epithelial transition (MET), which promotes conversion back to the parent cell morphology and growth of macrometastsis in the target organ. The unique biology of metastases once established in the brain, and in particular the "sanctuary" role that the brain microenvironment plays in promoting metastatic growth and treatment resistance, will also be examined. These issues are of more than academic interest since as systemic therapies gradually improve local tumor control, the relative impact of brain metastasis will inexorably play a proportionally greater role in determining patient morbidity and mortality.

Characterization of the melanoma brain metastatic niche in mice and humans

Brain metastases occur in 15% of patients with melanoma and are associated with a dismal prognosis. Here, we investigate the architectural phenotype and stromal reaction of melanoma brain metastasis in mice and humans. A syngeneic, green fluorescence protein (GFP)-expressing murine B16-F1 melanoma clone was introduced via intracardiac injection, and was examined in vivo in comparison with human specimens. Immunofluorescence analyses of the brain metastases revealed that F4/80⁺ macrophages/microglia were most abundant at the tumor front, but rare in its core, where they were found only around blood vessels (P = 0.01). Similar pattern of infiltration was found in CD3⁺ T cells (P < 0.01). Infiltrating T cells were prominently CD4⁺ compared with CD8⁺ T cells (P < 0.001). Blood vessels (CD31⁺) were less abundant at the tumor front than in its center (12 ± 1 vs. 4 ± 0.6 vessels per high-power field [HPF], P < 0.001). In contrast, there were few vessels at the tumor front, but their diameter was significantly larger at the front (8236 μm² vs. 4617 μm² average cross-sectional area, P < 0.005). This is the first comparative analysis of melanoma brain metastases showing similar stromal reaction in murine models and human specimens. Our results validate the utility of this murine model of melanoma brain metastases for investigating the mechanism of the human disease.

Myeloid-derived suppressor cells and anti-tumor T cells: a complex relationship

Myeloid-Derived Suppressor Cells (MDSC) are immature myeloid cells that are potent inhibitors of immune cell function and which accumulate under conditions of inflammation, especially cancer. MDSC are suggested to promote the growth of cancer by both enhancement of tumor angiogenesis and metastasis and also inhibition of antitumor immune responses. The presence of deficient and/or defective antitumor adaptive and innate immune responses, coincident with accumulation of MDSC in lymphoid organs and tumor parenchyma, supports the notion of a causal relationship. The potent ability of MDSC to inhibit several components and phases of immune response highlights the likelihood that targeting the inhibitory functions of MDSC may maximize the therapeutic potential of antitumor immunotherapy. In order to guide the rational development of immunotherapeutic strategies that incorporate inhibition of MDSC activity and enzymatic functions, thorough understanding of the role of MDSC in antitumor immune responses is required. In this manuscript we review the multifaceted inhibitory functions of MDSC and consider the role of MDSC-induced inhibition of antitumor T cell effector phase. Support for this research is from NIH R01 CA108573.

Anti-matrix metalloproteinase-9 DNAzyme decreases tumor growth in the MMTV-PyMT mouse model of breast cancer

INTRODUCTION

Despite continued improvements in diagnosis, surgical techniques, and chemotherapy, breast cancer patients are still overcome by cancer metastasis. Tumor cell proliferation, invasion and metastasis are mediated, at least in part, through degradation of basement membrane by neutral matrix metalloproteinases (MMP) produced by tumor and stromal cells. Evidence suggests that MMP-9 plays a significant role in breast tumor cell invasion and metastasis. DNAzymes or catalytic oligonucleotides are new classes of gene targeting molecules that bind and cleave a specific mRNA, resulting in decreased protein expression.

METHODS

The application of anti-MMP-9 DNAzyme (AM9D) for the treatment of primary and metastatic breast cancer was evaluated in vitro and in vivo using MDA-MB-231 cells and the MMTV-PyMT transgenic breast cancer mouse model. Spontaneously developed mammary tumors in MMTV-PyMT transgenic mice were treated intratumorally with naked AM9D, once a week for 4 weeks. The stability of DNAzyme was determined in vitro and in vivo using fluorescently labeled DNAzyme.

RESULTS

AM9D specifically inhibited expression of MMP-9 in MDA-MB-231 cells resulting in reduced invasive property of these cells by 43%. Weekly intratumoral treatment of spontaneously developed mammary tumors in MMTV-PyMT transgenic mice was sufficient to significantly reduce the rate of tumor growth and final tumor load in a dose dependent and statistically significant manner (P < 0.05). This decrease in tumor growth was correlated with decreased MMP-9 protein production within the treated tumor tissues. Tumors treated with AM9D were also less vascularized and contained more apoptotic cells compared to control and untreated tumors.

CONCLUSIONS

These results show that targeting and down regulation of MMP-9 by AM9D could prove useful as a therapy against breast carcinoma tumor growth and invasion.

Targeting tumor-infiltrating macrophages decreases tumor-initiating cells, relieves immunosuppression, and improves chemotherapeutic responses

Tumor-infiltrating immune cells can promote chemoresistance and metastatic spread in aggressive tumors. Consequently, the type and quality of immune responses present in the neoplastic stroma are highly predictive of patient outcome in several cancer types. In addition to host immune responses, intrinsic tumor cell activities that mimic stem cell properties have been linked to chemoresistance, metastatic dissemination, and the induction of immune suppression. Cancer stem cells are far from a static cell population; rather, their presence seems to be controlled by highly dynamic processes that are dependent on cues from the tumor stroma. However, the impact immune responses have on tumor stem cell differentiation or expansion is not well understood. In this study, we show that targeting tumor-infiltrating macrophages (TAM) and inflammatory monocytes by inhibiting either the myeloid cell receptors colony-stimulating factor-1 receptor (CSF1R) or chemokine (C-C motif) receptor 2 (CCR2) decreases the number of tumor-initiating cells (TIC) in pancreatic tumors. Targeting CCR2 or CSF1R improves chemotherapeutic efficacy, inhibits metastasis, and increases antitumor T-cell responses. Tumor-educated macrophages also directly enhanced the tumor-initiating capacity of pancreatic tumor cells by activating the transcription factor STAT3, thereby facilitating macrophage-mediated suppression of CD8(+) T lymphocytes. Together, our findings show how targeting TAMs can effectively overcome therapeutic resistance mediated by TICs.

Pro-metastatic tumor–stroma interactions in breast cancer

The vast majority of breast cancer-related deaths are due to metastatic disease. Reciprocal and complex interactions between epithelial tumor cells and the various components of the tumor microenvironment influence tumor progression and metastases although the molecular mechanisms underlying these metastasis-promoting effects are not fully characterized. Identifying and understanding pathways of tumor–stroma cross-talk are likely to lead to the development of novel prognostic biomarkers for metastasis and strategies to prevent metastasis at its earliest stages, resulting in improved patient outcomes.