C-C chemokine receptor 5 on pulmonary fibrocytes facilitates migration and promotes metastasis via matrix metalloproteinase 9

CCR5 promoter polymorphisms associated with nonsmall cell lung cancer

C-C chemokine receptor 5 (CCR5) plays a crucial role in the regulation of immune cell activation and migration as well as the progression of many cancers. We performed an in silico analysis using public data resources and found that the lung cancer patients with higher CCR5 expression had a notably better overall survival than those with lower CCR5 expression patients and CCR5 expression level is positive correlated with the infiltration of immune cells, such as B, CD8+ T and CD4+ T cells, in both lung adenocarcinoma and lung squamous cell cancer. In the present study, we investigated the association between the promoter polymorphism of CCR5 and nonsmall cell lung cancer (NSCLC). A case-control study of 449 NSCLC patients and 516 controls of Chinese Han population was conducted, along with polymorphism detection using a sequencing method. A dual-luciferase reporter assay system was used to analyse the transcriptional activity of CCR5 promoter variations. Our results showed that the frequency of rs1799987-AA was significantly higher in the NSCLC group than in the controls in recessive model (p = .007, OR = 1.66 95% confidence interval [CI]: 1.14-2.40, adjusted by sex and age); the G allele showed a significant associated with NSCLC in dominant model (p = .003, OR = 1.64, 95%CI: 1.18-2.28, adjusted by sex and age). Compared with haplotype H1 rs2227010-rs2734648-rs1799987-rs1799988-rs1800023-rs1800024: A-T-G-T-G-C, haplotype H5: A-G-G-T-G-C increased the risk of NSCLC by over 10-fold (p < .0001, OR = 16.09, 95%CI: 5.37-48.20, adjusted by sex and age) and notably depressed the transcriptional activity of the CCR5 promoter in 293T, A549, H1299 and HeLa cells. In conclusion, CCR5 promoter polymorphisms are significantly associated with NSCLC by affecting the transcriptional activity of the CCR5 promoter.

Weaving the nest: extracellular matrix roles in pre-metastatic niche formation

The discovery that primary tumors condition distant organ sites of future metastasis for seeding by disseminating tumor cells through a process described as the pre-metastatic niche (PMN) formation revolutionized our understanding of cancer progression and opened new avenues for therapeutic interventions. Given the inherent inefficiency of metastasis, PMN generation is crucial to ensure the survival of rare tumor cells in the otherwise hostile environments of metastatic organs. Early on, it was recognized that preparing the "soil" of the distal organ to support the outgrowth of metastatic cells is the initiating event in PMN development, achieved through the remodeling of the organ's extracellular matrix (ECM). Remote restructuring of ECM at future sites of metastasis under the influence of primary tumor-secreted factors is an iterative process orchestrated through the crosstalk between resident stromal cells, such as fibroblasts, epithelial and endothelial cells, and recruited innate immune cells. In this review, we will explore the ECM changes, cellular effectors, and the mechanisms of ECM remodeling throughout PMN progression, as well as its impact on shaping the PMN and ultimately promoting metastasis. Moreover, we highlight the clinical and translational implications of PMN ECM changes and opportunities for therapeutically targeting the ECM to hinder PMN formation.

CCL3 Promotes Proliferation of Colorectal Cancer Related with TRAF6/NF-κB Molecular Pathway

Chemokine C-C motif chemokine ligand 3 (CCL3) plays an important role in the invasion and metastasis of malignant tumors. For developing new therapeutic targets and antitumor drugs, the effect of chemokine CCL3 and the related cytokine network on colorectal cancer should be investigated. This study used cell, tissue, and animal experiments to prove that CCL3 is highly expressed in colorectal cancer and confirmed that CCL3 can promote the proliferation of cancer cells, and its expression is closely related to TRAF6/NF-κB molecular pathway. In addition, protein chip technology was used to examine colorectal cancer tissue samples and identify the key factors of chemokine CCL3 and the toll-like receptors/nuclear factor-κB (TLR/NF-κB) pathway in cancer and metastatic lymph nodes. Furthermore, the lentiviral vector technology was employed for transfection to construct interference and overexpression cell lines. The experimental results reveal the mechanism of CCL3 and TNF receptor-associated factor 6 (TRAF6)/NF-κB pathway-related factors and their effects on the proliferation of colon cancer cells. Finally, the expression and significance of CCL3 in colorectal cancer tissues and its correlation with clinical pathology were studied by immunohistochemistry. Also, the results confirmed that CCL3 and C-C motif chemokine receptor 5 (CCR5) were expressed in adjacent tissues, colorectal cancer tissues, and metastatic cancer. The expression level was correlated with the clinical stage and nerve invasion. The expression of chemokine CCL3 and receptor CCR5 was positively correlated with the expression of TRAF6 and NF-κB and could promote the proliferation, invasion, and migration of colorectal cancer cells through TRAF6 and NF-κB.

Fibrocytes in the Tumor Microenvironment

Tumors have long been compared to chronic wounds that do not heal, since they share many of the same molecular and cellular processes. In normal wounds, healing processes lead to restoration of cellular architecture, while in malignant tumors, these healing processes become dysregulated and contribute to growth and invasion of neoplastic cells into the surrounding tissues. Fibrocytes are fibroblast-like cells that differentiate from bone marrow-derived CD14+ circulating monocytes and aid wound healing. Although most monocytes will differentiate into macrophages after extravasating into a tissue, signals present in a wound environment can cause some monocytes to differentiate into fibrocytes. The fibrocytes secrete matrix proteins and inflammatory cytokines, activate local fibroblasts to proliferate and increase extracellular matrix production, and promote angiogenesis, and because fibrocytes are contractile, they also help wound contraction. There is now emerging evidence that fibrocytes are present in the tumor microenvironment, attracted by the chronic tissue damage and cytokines from both cancer cells and other immune cells. Fibrocytes may aid in the survival and spread of neoplastic cells, so these wound-healing cells may be a promising target for anticancer research in future studies.

Chemokines in breast cancer: Regulating metabolism

Accumulating evidence indicates that chemokine-chemokine receptor interactions invoke biological responses beyond their originally described function of orchestrating leukocyte trafficking. In this review we will extend the findings that chemokines participate actively in the neoplastic process, and consider the contribution of CCL5 activation of CCR5 on breast cancer cells to upregulation of anabolic metabolic events that would support the energy demands of cell replication and proliferation.

The Role of MMP8 in Cancer: A Systematic Review

Matrix metalloproteinases (MMPs) have traditionally been considered as tumor promoting enzymes as they degrade extracellular matrix components, thus increasing the invasion of cancer cells. It has become evident, however, that MMPs can also cleave and alter the function of various non-matrix bioactive molecules, leading to both tumor promoting and suppressive effects. We applied systematic review guidelines to study MMP8 in cancer including the use of MMP8 as a prognostic factor or as a target/anti-target in cancer treatment, and its molecular mechanisms. A total of 171 articles met the inclusion criteria. The collective evidence reveals that in breast, skin and oral tongue cancer, MMP8 inhibits cancer cell invasion and proliferation, and protects patients from metastasis via cleavage of non-structural substrates. Conversely, in liver and gastric cancers, high levels of MMP8 worsen the prognosis. Expression and genetic alterations of MMP8 can be used as a prognostic factor by examination of the tumor and serum/plasma. We conclude, that MMP8 has differing effects on cancers depending on their tissue of origin. The use of MMP8 as a prognostic factor alone, or with other factors, seems to have potential. The molecular mechanisms of MMP8 in cancer further emphasize its role as an important regulator of bioactive molecules.

High expression of CCR5 in melanoma enhances epithelial-mesenchymal transition and metastasis via TGFβ1

Chemokine receptors are highly expressed in various cancers and play crucial roles in tumor progression. However, their expression patterns and functions in melanoma are unclear. The present study aimed to identify the chemokine receptors that play critical roles in melanoma progression and unravel the underlying molecular mechanisms. We found that CCR5 was more abundant in melanoma cells than normal cells and was positively associated with tumor malignancy in clinical patients. Animal experiments suggested that CCR5 deficiency in B16/F10 or A375 cells suppressed primary tumor growth and lung metastasis, whereas CCR5 overexpression in B16/F0 cells enhanced primary tumor growth and lung metastasis. CCR5 played a critical role in proliferation and migration of melanoma cells in vitro. Importantly, CCR5 was required for maintenance of the mesenchymal phenotype of metastatic melanoma cells. Mechanistically, CCR5 positively regulated expression of TGFβ1, which in turn induced epithelial-mesenchymal transition and migration via PI3K/AKT/GSK3β signaling. Collectively, our results establish a critical role of CCR5 expressed by melanoma cells in cancer progression and reveal the novel mechanisms controlling this process, which suggests the prognostic value of CCR5 in melanoma patients and provides novel insights into CCR5-targeted strategies for melanoma treatment. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Biology and Therapeutic Implications of Tumor Dormancy and Reactivation

Advancements in the early detection of cancer coupled with improved surgery, radiotherapy, and adjuvant therapy led to substantial increase in patient survival. Nevertheless, cancer metastasis is the leading cause of death in several cancer patients. The majority of these deaths are associated with metastatic relapse kinetics after a variable period of clinical remission. Most of the cancer recurrences are thought to be associated with the reactivation of dormant disseminated tumor cells (DTCs). In this review, we have summarized the cellular and molecular mechanisms related to DTCs and the role of microenvironmental niche. These mechanisms regulate the dormant state and help in the reactivation, which leads to metastatic outgrowth. Identification of novel therapeutic targets to eliminate these dormant tumor cells will be highly useful in controlling the metastatic relapse-related death with several cancers.

Pre-metastatic niches: organ-specific homes for metastases

It is well established that organs of future metastasis are not passive receivers of circulating tumour cells, but are instead selectively and actively modified by the primary tumour before metastatic spread has even occurred. Sowing the 'seeds' of metastasis requires the action of tumour-secreted factors and tumour-shed extracellular vesicles that enable the 'soil' at distant metastatic sites to encourage the outgrowth of incoming cancer cells. In this Review, we summarize the main processes and new mechanisms involved in the formation of the pre-metastatic niche.

Chemokine Receptor Signaling and the Hallmarks of Cancer

The chemokines are a family of chemotactic cytokines that mediate their activity by acting on seven-transmembrane-spanning G protein-coupled receptors. Both the ability of the chemokines and their receptors to form homo- and heterodimers and the promiscuity of the chemokine-chemokine receptor interaction endow this protein family with enormous signaling plasticity and complexity that are not fully understood at present. Chemokines were initially identified as essential regulators of homeostatic and inflammatory trafficking of innate and adaptive leucocytes from lymphoid organs to tissues. Chemokines also mediate the host response to cancer. Nevertheless, chemokine function in this response is not limited to regulating leucocyte infiltration into the tumor microenvironment. It is now known that chemokines and their receptors influence most-if not all-hallmark processes of cancer; they act on both neoplastic and untransformed cells in the tumor microenvironment, including fibroblasts, endothelial cells (blood and lymphatic), bone marrow-derived stem cells, and, obviously, infiltrating leucocytes. This review begins with an overview of chemokine and chemokine receptor structure, to better define how chemokines affect the proliferation, survival, stemness, and metastatic potential of neoplastic cells. We also examine the main mechanisms by which chemokines regulate tumor angiogenesis and immune cell infiltration, emphasizing the pro- and antitumorigenic activity of this protein superfamily in these interrelated processes.

Mesenchymal stem cells as a double-edged sword in suppression or progression of solid tumor cells

Tumor cells are able to attract mesenchymal stem cells (MSCs) to primary tumor site. On the other hand, MSCs secrete various factors to attract tumor cells towards BM. In this review, in addition to assessment of MSCs function at tumor sites and their impact on growth and metastasis of tumor cells, the importance of MSC in attraction of malignant cells to BM and their involvement in drug resistance of tumor cells have also been studied. Relevant literature was identified by a PubMed search (2000-2015) of English-language literature using the terms mesenchymal stem cells, cancer cell, metastasis, and tumor microenvironment. MSCs migrate towards tumor microenvironment and are involved in both pro-tumorigenic and antitumorigenic functions. The dual function of MSCs at tumor sites is dependent upon a variety of factors, including the type and origin of MSCs, the cancer cell line under study, in vivo or in vitro conditions, the factors secreted by MSCs and interactions between MSCs, host immune cells and cancer cells. Therefore, MSCs can be regarded both as friends and enemies of cancer cells. Although the role of a number of pathways, including IL-6/STAT3 pathway, has been indicated in controlling the interaction between MSCs and tumor cells, other mechanisms by which MSCs can control the tumor cells are not clear yet. A better understanding of these mechanisms through further studies can determine the exact role of MSCs in cancer progression and identify them as important therapeutic agents or targets.

Fibrocytes Differ from Macrophages but Can Be Infected with HIV-1

Fibrocytes (fibroblastic leukocytes) are recently identified as unique hematopoietic cells with features of both macrophages and fibroblasts. Fibrocytes are known to contribute to the remodeling or fibrosis of various injured tissues. However, their role in viral infection is not fully understood. In this study, we show that differentiated fibrocytes are phenotypically distinguishable from macrophages but can be infected with HIV-1. Importantly, fibrocytes exhibited persistently infected cell-like phenotypes, the degree of which was more apparent than macrophages. The infected fibrocytes produced replication-competent HIV-1, but expressed HIV-1 mRNA at low levels and strongly resisted HIV-1-induced cell death, which enabled them to support an extremely long-term HIV-1 production at low but steady levels. More importantly, our results suggested that fibrocytes were susceptible to HIV-1 regardless of their differentiation state, in contrast to the fact that monocytes become susceptible to HIV-1 after the differentiation into macrophages. Our findings indicate that fibrocytes are the previously unreported HIV-1 host cells, and they suggest the importance of considering fibrocytes as one of the long-lived persistently infected cells for curing HIV-1.

Classification and biology of tumour associated stromal cells

Stroma is a fundamental component of the tumour microenvironment whereby it supports malignant cell growth and spreading. It consists of different entities including cells of the immune system, vascular structures and fibroblasts. Much attention has recently been paid to fibroblasts since there is compelling evidence that they orchestrate the recruitment of and educate other cells to promote cancer growth. This review proposes to discuss in detail the nomenclature, origin, and biological functions of the different stromal cells residing in tumours.

Role of platelet-derived growth factor/platelet-derived growth factor receptor axis in the trafficking of circulating fibrocytes in pulmonary fibrosis

Circulating fibrocytes have been reported to migrate into the injured lungs, and contribute to fibrogenesis via CXCL12-CXCR4 axis. In contrast, we report that imatinib mesylate prevented bleomycin (BLM)-induced pulmonary fibrosis in mice by inhibiting platelet-derived growth factor receptor (PDGFR), even when it was administered only in the early phase. The goal of this study was to test the hypothesis that platelet-derived growth factor (PDGF) might directly contribute to the migration of fibrocytes to the injured lungs. PDGFR expression in fibrocytes was examined by flow cytometry and RT-PCR. The migration of fibrocytes was evaluated by using a chemotaxis assay for human fibrocytes isolated from peripheral blood. The numbers of fibrocytes triple-stained for CD45, collagen-1, and CXCR4 were also examined in lung digests of BLM-treated mice. PDGFR mRNA levels in fibrocytes isolated from patients with idiopathic pulmonary fibrosis were investigated by real-time PCR. Fibrocytes expressed both PDGFR-α and -β, and migrated in response to PDGFs. PDGFR inhibitors (imatinib, PDGFR-blocking antibodies) suppressed fibrocyte migration in vitro, and reduced the number of fibrocytes in the lungs of BLM-treated mice. PDGF-BB was a stronger chemoattractant than the other PDGFs in vitro, and anti-PDGFR-β-blocking antibody decreased the numbers of fibrocytes in the lungs compared with anti-PDGFR-α antibody in vivo. Marked expression of PDGFR-β was observed in fibrocytes from patients with idiopathic pulmonary fibrosis compared with healthy subjects. These results suggest that PDGF directly functions as a strong chemoattractant for fibrocytes. In particular, the PDGF-BB-PDGFR-β biological axis might play a critical role in fibrocyte migration into the fibrotic lungs.

Chemokine receptors and their therapeutic opportunities in diseased lung: far beyond leukocyte trafficking

Chemokine receptors and their chemokine ligands, key mediators of inflammatory and immune cell trafficking, are involved in the regulation of both physiological and pathological processes in the lung. The discovery that chemokine receptors/chemokines, typically expressed by inflammatory and immune cells, are also expressed in structural lung tissue cells suggests their role in mediating the restoration of lung tissue structure and functions. Thus, chemokine receptors/chemokines contribute not only to inflammatory and immune responses in the lung but also play a critical role in the regulation of lung tissue repair, regeneration, and remodeling. This review aims to summarize current state-of-the-art on chemokine receptors and their ligands in lung diseases such as chronic obstructive pulmonary disease, asthma/allergy, pulmonary fibrosis, acute lung injury, and lung infection. Furthermore, the therapeutic opportunities of chemokine receptors in aforementioned lung diseases are discussed. The review also aims to delineate the potential contribution of chemokine receptors to the processes leading to repair/regeneration of the lung tissue.

Flow Cytometric Identification of Fibrocytes in the Human Circulation

Because the incidence of organ fibrosis increases with age, various fibrosing disorders are projected to account for significant increases in morbidity, mortality, and healthcare costs in the years to come. Treatments for these diseases are scarce and better understanding of the immunopathogenesis of fibrosis and its relationship to aging are sorely needed. One area of interest in this field is the role that fibrocytes might play in the development of tissue remodeling and fibrosis. Fibrocytes are mesenchymal progenitor cells presumed to be of monocyte origin that possess the tissue remodeling properties of tissue resident fibroblasts such as extracellular matrix production and α-SMA-related contractile properties, as well as the immunologic functions typically attributed to macrophages including production of cytokines and chemokines, antigen presentation, regulation of leukocyte trafficking, and modulation of angiogenesis. Fibrocytes could participate in the development of age-related fibrosing disorders through any or all of these functions. This chapter presents methods that have been developed for the study of circulating human fibrocytes. Protocols for the quantification of fibrocytes in the human circulation will be presented along with discussion of the technical challenges that are frequently encountered in this field. It is hoped that this information will facilitate further investigation of the relationship between fibrocytes, aging, and fibrosis, and perhaps uncover new areas of study in these difficult-to-treat and deadly diseases.

Origin of myofibroblasts and cellular events triggering fibrosis

Renal fibrosis is a major hallmark of chronic kidney disease that is considered to be a common end point of various types of renal disease. To date, the biological meaning of fibrosis during the progression of chronic kidney diseases is unknown and possibly depends on the cell type contributing to extracellular matrix production. During the past decade, the origin of myofibroblasts in the kidney has been intensively investigated. Determining the origins of renal myofibroblasts is important because these might account for the heterogeneous characteristics and behaviors of myofibroblasts. Current data strongly suggest that collagen-producing myofibroblasts in the kidney can be derived from various cellular sources. Resident renal fibroblasts and cells of hematopoietic origin migrating into the kidney seem to be the most important ancestors of myofibroblasts. It is likely that both cell types communicate with each other and also with other cell types in the kidney. In this review, we will discuss the current knowledge on the origin of scar-producing myofibroblasts and cellular events triggering fibrosis.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Paracrine functions of fibrocytes to promote lung fibrosis

Fibrocytes are derived from the bone marrow and are found in the circulation. They can be recruited to sites of injury and contribute to repair/remodeling. In vitro evidence suggests that fibrocytes may differentiate into fibroblasts to promote lung fibrosis. However, in vivo evidence for this is sparse. This review summarizes recent literature which may suggest that fibrocytes function to promote fibrosis via paracrine actions. In this way, secretion of growth factors, proteases and matricellular proteins may strongly influence the actions of resident epithelial and mesenchymal cells to promote repair and resolution or to tip the scale toward pathologic remodeling.

C-C chemokine receptor 5 on pulmonary mesenchymal cells promotes experimental metastasis via the induction of erythroid differentiation regulator 1

C-C Chemokine receptor 5 knockout (Ccr5(-/-)) mice develop fewer experimental pulmonary metastases than wild-type (WT) mice. This phenomenon was explored by applying gene expression profiling to the lungs of mice with these metastases. Consequently, erythroid differentiation regulator 1 (Erdr1) was identified as upregulated in the WT mice. Though commonly associated with bone marrow stroma, Erdr1 was differentially expressed in WT pulmonary mesenchymal cells (PMC) and murine embryonic fibroblasts (MEF). Moreover, the Ccr5 ligand Ccl4 increased its expression by 3.36 ± 0.14-fold. Ccr5 signaling was dependent on the mitogen-activated protein kinase kinase (Map2k) but not the phosphoinositide 3-kinase (Pi3k) pathway because treatment with U0126 inhibited upregulation of Erdr1, but treatment with LY294002 increased the expression by 3.44 ± 0.92-fold (P < 0.05). The effect Erdr1 on B16-F10 melanoma metastasis was verified by the adoptive transfer of WT MEFs into Ccr5(-/-) mice. In this model, MEFs that had been transduced with Erdr1 short hairpin RNA (shRNA) lowered metastasis by 33% compared with control transduced MEFs. The relevance of ERDR1 on human disease was assessed by coculturing chronic lymphocytic leukemia (CLL) cells with M2-10B4 stromal cells that had been transfected with shRNA or control plasmids. After 96 hours of coculture, the cell counts were higher with control cell lines than with Erdr1 knockdown lines [odds ratio (OR), 1.88 ± 0.27, 2.52 ± 0.66, respectively]. This increase was associated with a decrease in apoptotic cells (OR, 0.69 ± 0.18, 0.58 ± 0.12, respectively).

IMPLICATIONS

Therefore, ERDR1 is a stromal-derived factor that promotes cancer cell survival in vitro and in an experimental metastasis model.

Circulating fibrocytes prepare the lung for cancer metastasis by recruiting Ly-6C+ monocytes via CCL2

Fibrocytes are circulating, hematopoietic cells that express CD45 and Col1a1. They contribute to wound healing and several fibrosing disorders by mechanisms that are poorly understood. In this report, we demonstrate that fibrocytes predispose the lung to B16-F10 metastasis by recruiting Ly-6C(+) monocytes. To do so, we isolated fibrocytes expressing CD45, CD11b, CD13, and Col1a1 from the lungs of wild type (WT) and Ccr5(-/-) mice. WT but not Ccr5(-/-) fibrocytes increased the number of metastatic foci when injected into Ccr5(-/-) mice (73 ± 2 versus 32 ± 5; p < 0.001). This process was MMP9 dependent. Injection of WT enhanced GFP(+) fibrocytes also increased the number of Gr-1(Int), CD11b(+), and enhanced GFP(-) monocytes. Like premetastatic-niche monocytes, these recruited cells expressed Ly-6C, CD117, and CD45. The transfer of these cells into Ccr5(-/-) mice enhanced metastasis (90 ± 8 foci) compared with B cells (27 ± 2), immature dendritic cells (31 ± 6), or alveolar macrophages (28 ± 3; p < 0.05). WT and Ccl2(-/-) fibrocytes also stimulated Ccl2 expression in the lung by 2.07 ± 0.05- and 2.78 ± 0.36-fold compared with Ccr5(-/-) fibrocytes (1.0 ± 0.06; p < 0.05). Furthermore, WT fibrocytes did not increase Ly-6C(+) monocytes in Ccr2(-/-) mice and did not promote metastasis in either Ccr2(-/-) or Ccl2(-/-) mice. These data support our hypothesis that fibrocytes contribute to premetastatic conditioning by recruiting Ly-6C(+) monocytes in a chemokine-dependent process. This work links metastatic risk to conditions that mobilize fibrocytes, such as inflammation and wound repair.

Fibrocytes develop outside the kidney but contribute to renal fibrosis in a mouse model

Collagen-producing bone marrow-derived cells (fibrocytes) have been detected in animal models and patients with fibrotic diseases. In vitro data suggest that they develop from monocytes with the help of accessory cells and profibrotic soluble factors. Using a mouse model of renal fibrosis, unilateral ureteral obstruction, we found the number of circulating fibrocytes was not reduced when monocytes were depleted with a monoclonal antibody against CCR2 or when CCR2-/- mice with very low numbers of circulating or splenic monocytes were analyzed. The absence of CCR2, however, interfered with migration of fibrocytes into the kidney. The phenotype of splenic and renal fibrocytes was very similar and distinct from classical monocytes as fibrocytes expressed no CD115, medium levels of CCR2, and high levels of CD11b and Ly-6G. Using a depleting monoclonal antibody against Ly-6G or bone marrow chimeric mice expressing the diphtheria toxin receptor under the control of CD11b, we could efficiently deplete fibrocytes from the kidney. Depletion of fibrocytes or reduced migration of fibrocytes into the kidney resulted in lower renal expression of collagen-I. Thus, fibrocytes develop outside the kidney independent of infiltrating monocytes and rely on CCR2 for migration into target organs.

The metastatic niche and stromal progression

The tumor stroma is comprised of extracellular matrix, non-malignant cells, and the signaling molecules they produce. It is an integral and vital component of primary tumors that together with the underlying genetic defects in the tumor cells determines the growth characteristics, morphology, and invasiveness of the tumor. In parallel to continuing genetic changes in the tumor cells themselves, the tumor stroma progressively evolves during primary tumor development. Cancer cells that disseminate from primary tumors are dependent on this stromal microenvironment, and therefore the microenvironment they encounter at secondary sites determines their fate. For those cells that survive at these sites, stromal progression can serve to re-establish a supportive tumor stroma, fostering the outgrowth of the cells as metastases. Formation of a metastatic niche that supports the survival and growth of disseminated tumor cells is a key feature of this stromal progression. The endogenous organ microenvironment can provide components of the metastatic niche. In addition, microenvironmental changes in organs prior to receipt of disseminated tumor cells can be induced by factors secreted systemically by primary tumors, causing the formation of pre-metastatic niches. Further maturation of metastatic niches can be responsible for the re-activation of dormant disseminated tumor cells many years after removal of the primary tumor. The concept of the metastatic niche and stromal progression has profound consequences for our understanding of metastatic disease, and promises to open up new strategies for the diagnosis, prognostic evaluation, and therapy of cancer.

Activated T cell exosomes promote tumor invasion via Fas signaling pathway

Activated T cells release bioactive Fas ligand (FasL) in exosomes, which subsequently induce self-apoptosis of T cells. However, their potential effects on cell apoptosis in tumors are still unknown. In this study, we purified exosomes expressing FasL from activated CD8(+) T cell from OT-I mice and found that activated T cell exosomes had little effect on apoptosis and proliferation of tumor cells but promoted the invasion of B16 and 3LL cancer cells in vitro via the Fas/FasL pathway. Activated T cell exosomes increased the amount of cellular FLICE inhibitory proteins and subsequently activated the ERK and NF-κB pathways, which subsequently increased MMP9 expression in the B16 murine melanoma cells. In a tumor-invasive model in vivo, we observed that the activated T cell exosomes promoted the migration of B16 tumor cells to lung. Interestingly, pretreatment with FasL mAb significantly reduced the migration of B16 tumor cells to lung. Furthermore, CD8 and FasL double-positive exosomes from tumor mice, but not normal mice, also increased the expression of MMP9 and promoted the invasive ability of B16 murine melanoma and 3LL lung cancer cells. In conclusion, our results indicate that activated T cell exosomes promote melanoma and lung cancer cell metastasis by increasing the expression of MMP9 via Fas signaling, revealing a new mechanism of tumor immune escape.

Fibrocytes: emerging effector cells in chronic inflammation

Fibrocytes are unique cells possessing the proinflammatory properties of macrophages and the tissue remodeling properties of fibroblasts. Because these cells display a strong association with many human diseases characterized by chronic and dysregulated inflammatory responses the study of fibrocytes is important and timely. This review presents recent data regarding fibrocyte origin, identification, differentiation, and appearance in diseased tissue. The available data regarding the association of fibrocytes with several forms of chronic tissue inflammation seen in the setting of lung disease, autoimmunity, liver disease, and normal aging will be presented. This review concludes by putting these data in perspective and by suggesting future areas of investigation. It is hoped that this information will lead to additional investigations in this burgeoning field and improve our understanding of the novel role fibrocytes may play in human disease.

An isolated tumor perfusion model in mice

The role of stromal cells in the tumor microenvironment has been extensively characterized. We and others have shown that stromal cells may participate in several steps of the metastatic cascade. This protocol describes an isolated tumor perfusion model that enables studies of cancer and stromal cell shedding. It could also be used to study the effects of therapies interfering with the shedding of tumor cells or fragments, circulating (stem) cells or biomarkers. Primary tumors are grown in a microenvironment in which stromal cells express GFP ubiquitously. Tumors are implanted orthotopically or can be implanted ectopically. As a result, all tumor-associated stromal cells express GFP. This technique can be used to detect and study the role of stromal cells in tumor fragments within the circulation in mice. Studying the role of stromal cells in circulating tumor fragments using this model may take 2-10 weeks, depending on the growth rate of the primary tumor.

A transient parabiosis skin transplantation model in mice

Parabiosis-conjoined surgery to provide a shared circulation between two mice-has been previously developed to study the hematopoietic system. This protocol describes the use of parabiosis for efficient transplantation of skin from a transgenic to a wild-type mouse. It can be used to study the role of stromal cells in a spontaneous model of distant cancer dissemination (metastasis). We have recently shown that primary tumor-derived stromal cells may facilitate metastasis by providing a provisional stroma at the secondary site. Studying the role of primary tumor-derived stroma cells requires methods for distinguishing and targeting stromal cells originating from the primary tumor versus their counterparts in the metastatic site. Parabiosis may also be used, taking advantage of the shared circulation between the parabiosed mice, to study tumor metastasis from one parabiont to another, or to investigate the role of circulating inflammatory cells or stem cells. Studying the role of stromal cells in metastasis using this model typically takes up to 11 weeks.

The role of fibrocytes in sickle cell lung disease

Background

Interstitial lung disease is a frequent complication in sickle cell disease and is characterized by vascular remodeling and interstitial fibrosis. Bone marrow-derived fibrocytes have been shown to contribute to the pathogenesis of other interstitial lung diseases. The goal of this study was to define the contribution of fibrocytes to the pathogenesis of sickle cell lung disease.

Methodology/Principal Findings

Fibrocytes were quantified and characterized in subjects with sickle cell disease or healthy controls, and in a model of sickle cell disease, the NY1DD mouse. The role of the chemokine ligand CXCL12 in trafficking of fibrocytes and phenotype of lung disease was examined in the animal model. We found elevated concentration of activated fibrocytes in the peripheral blood of subjects with sickle cell disease, which increased further during vaso-occlusive crises. There was a similar elevations in the numbers and activation phenotype of fibrocytes in the bone marrow, blood, and lungs of the NY1DD mouse, both at baseline and under conditions of hypoxia/re-oxygenation. In both subjects with sickle cell disease and the mouse model, fibrocytes expressed a hierarchy of chemokine receptors, with CXCR4 expressed on most fibrocytes, and CCR2 and CCR7 expressed on a smaller subset of cells. Depletion of the CXCR4 ligand, CXCL12, in the mouse model resulted in a marked reduction of fibrocyte trafficking into the lungs, reduced lung collagen content and improved lung compliance and histology.

Conclusions

These data support the notion that activated fibrocytes play a significant role in the pathogenesis of sickle cell lung disease.

Flow cytometric identification of fibrocytes in scleroderma lung disease

Scleroderma is an autoimmune disease characterized by the progressive and dysregulated accumulation of collagen in the skin and internal organs. Pulmonary complications including interstitial lung disease have emerged as the greatest cause of mortality in this disease. Because treatments are limited, new areas of investigation are sorely needed. An emerging area of interest in this field is a potential role for fibrocytes as biomarkers or mediators of disease. Fibrocytes are monocyte-derived mesenchymal progenitor cells that exhibit features of extracellular matrix production and wound contraction in addition to immunologic functions such as cytokine and chemokine production, antigen presentation, leukocyte trafficking, and modulation of angiogenesis. Fibrocytes could participate in the pathogenesis of scleroderma lung disease through any or all of these functions and may be useful biomarkers of disease activity. This chapter presents protocols that have been developed for the study of fibrocytes obtained from human circulation and tissues. Protocols for the quantification of fibrocytes in murine models also are described, along with discussion of common technical challenges. It is hoped that this information will allow further investigation of the role that fibrocytes might play in Scleroderma-related lung disease and perhaps lead to new areas of study in this difficult-to-treat and deadly disease.

The Chlamydia protease CPAF regulates host and bacterial proteins to maintain pathogen vacuole integrity and promote virulence

The obligate intracellular bacterial pathogen Chlamydia trachomatis injects numerous effector proteins into the epithelial cell cytoplasm to manipulate host functions important for bacterial survival. In addition, the bacterium secretes a serine protease, chlamydial protease-like activity factor (CPAF). Although several CPAF targets are reported, the significance of CPAF-mediated proteolysis is unclear due to the lack of specific CPAF inhibitors and the diversity of host targets. We report that CPAF also targets chlamydial effectors secreted early during the establishment of the pathogen-containing vacuole ("inclusion"). We designed a cell-permeable CPAF-specific inhibitory peptide and used it to determine that CPAF prevents superinfection by degrading early Chlamydia effectors translocated during entry into a preinfected cell. Prolonged CPAF inhibition leads to loss of inclusion integrity and caspase-1-dependent death of infected epithelial cells. Thus, CPAF functions in niche protection, inclusion integrity and pathogen survival, making the development of CPAF-specific protease inhibitors an attractive antichlamydial therapeutic strategy.

Chemokine (C-C motif) ligand 2 mediates direct and indirect fibrotic responses in human and murine cultured fibrocytes

Background

Fibrocytes are a population of circulating bone-marrow-derived cells that express surface markers for leukocytes and mesenchymal cells, and are capable of differentiating into myofibroblasts. They have been observed at sites of active fibrosis and increased circulating numbers correlate with mortality in idiopathic pulmonary fibrosis (IPF). Inhibition of chemokine (C-C motif) receptor 2 (CCR2) during experimental models of lung fibrosis reduces lung collagen deposition, as well as reducing lung fibrocyte accumulation. The aim of the present study was to determine whether human and mouse fibrocytes express functional CCR2.

Results

Following optimized and identical human and murine fibrocyte isolation, both cell sources were shown to be positive for CCR2 by flow cytometry and this expression colocalized with collagen I and CD45. Human blood fibrocytes stimulated with the CCR2 ligand chemokine (C-C motif) ligand 2 (CCL2), demonstrated increased proliferation (P < 0.005) and differentiation into myofibroblasts (P < 0.001), as well as a chemotactic response (P < 0.05). Murine fibrocytes also responded to CCR2 stimulation, with CCL12 being more potent than CCL2.

Conclusions

This study directly compares the functional responses of human and murine fibrocytes to CCR2 ligands, and following comparable isolation techniques. We have shown comparable biological effects, strengthening the translatability of the murine models to human disease with respect to targeting the CCR2 axis to ameliorate disease in IPF patients.

Fibrocytes: emerging effector cells in chronic inflammation

Fibrocytes are mesenchymal cells that arise from monocyte precursors. They are present in injured organs and have both the inflammatory features of macrophages and the tissue remodelling properties of fibroblasts. Chronic inflammatory stimuli mediate the differentiation, trafficking and accumulation of these cells in fibrosing conditions associated with autoimmunity, cardiovascular disease and asthma. This Opinion article discusses the immunological mediators controlling fibrocyte differentiation and recruitment, describes the association of fibrocytes with chronic inflammatory diseases and compares the potential roles of fibrocytes in these disorders with those of macrophages and fibroblasts. It is hoped that this information prompts new opportunities for the study of these unique cells.

The inflammasome component NLRP3 impairs antitumor vaccine by enhancing the accumulation of tumor-associated myeloid-derived suppressor cells

The inflammasome is a proteolysis complex that generates the active forms of the proinflammatory cytokines interleukin (IL)-1β and IL-18. Inflammasome activation is mediated by NLR proteins that respond to microbial and nonmicrobial stimuli. Among NLRs, NLRP3 senses the widest array of stimuli and enhances adaptive immunity. However, its role in antitumor immunity is unknown. Therefore, we evaluated the function of the NLRP3 inflammasome in the immune response using dendritic cell vaccination against the poorly immunogenic melanoma cell line B16-F10. Vaccination of Nlrp3(-/-) mice led to a relative 4-fold improvement in survival relative to control animals. Immunity depended on CD8(+) T cells and exhibited immune specificity and memory. Increased vaccine efficacy in Nlrp3(-/-) hosts did not reflect differences in dendritic cells but rather differences in myeloid-derived suppressor cells (MDSC). Although Nlrp3 was expressed in MDSCs, the absence of Nlrp3 did not alter either their functional capacity to inhibit T cells or their presence in peripheral lymphoid tissues. Instead, the absence of Nlrp3 caused a 5-fold reduction in the number of tumor-associated MDSCs found in host mice. Adoptive transfer experiments also showed that Nlrp3(-/-) MDSCs were less efficient in reaching the tumor site. Depleting MDSCs with an anti-Gr-1 antibody increased the survival of tumor-bearing wild-type mice but not Nlrp3(-/-) mice. We concluded that Nlrp3 was critical for accumulation of MDSCs in tumors and for inhibition of antitumor T-cell immunity after dendritic cell vaccination. Our findings establish an unexpected role for Nlrp3 in impeding antitumor immune responses, suggesting novel approaches to improve the response to antitumor vaccines by limiting Nlrp3 signaling.

Malignant cells facilitate lung metastasis by bringing their own soil

Metastatic cancer cells (seeds) preferentially grow in the secondary sites with a permissive microenvironment (soil). We show that the metastatic cells can bring their own soil--stromal components including activated fibroblasts--from the primary site to the lungs. By analyzing the efferent blood from tumors, we found that viability of circulating metastatic cancer cells is higher if they are incorporated in heterotypic tumor-stroma cell fragments. Moreover, we show that these cotraveling stromal cells provide an early growth advantage to the accompanying metastatic cancer cells in the lungs. Consistent with this hypothesis, we demonstrate that partial depletion of the carcinoma-associated fibroblasts, which spontaneously spread to the lung tissue along with metastatic cancer cells, significantly decreases the number of metastases and extends survival after primary tumor resection. Finally, we show that the brain metastases from lung carcinoma and other carcinomas in patients contain carcinoma-associated fibroblasts, in contrast to primary brain tumors or normal brain tissue. Demonstration of the direct involvement of primary tumor stroma in metastasis has important conceptual and clinical implications for the colonization step in tumor progression.

Hsa-miR-125a-3p and hsa-miR-125a-5p are downregulated in non-small cell lung cancer and have inverse effects on invasion and migration of lung cancer cells

Background

Two mature microRNAs (miRNAs), hsa-miR-125a-3p and hsa-miR-125a-5p (collectively referred to as hsa-miR-125a-3p/5p), are derived from 3' and 5' ends of pre-miR-125a, respectively. Although impaired regulation of hsa-miR-125a-5p has been observed in some tumors, the role of this miRNA in invasion and metastasis remains unclear, and few studies have examined the function of hsa-miR-125a-3p. In order to characterize the functions of hsa-miR-125a-3p/5p in invasion and metastasis of non-small cell lung cancer (NSCLC), we investigated the relationships between hsa-miR-125a-3p/5p expression and lymph node metastasis in NSCLC tissues. We also explored the impact of expression of these miRNAs on invasive and migratory capabilities of lung cancer cells.

Methods

Expression of hsa-miR-125a-3p/5p in NSCLC tissues was explored using real-time PCR. The relationships between hsa-miR-125a-3p/5p expression and pathological stage or lymph node metastasis were assessed using the Spearman correlation test. For in vitro studies, lung cancer cells were transfected with sense and antisense 2'-O-methyl oligonucleotides for gain-of-function and loss-of-function experiments. Transwell experiments were performed to evaluate cellular migration and invasion.

Results

Expression of hsa-miR-125a-3p/5p was lower in NSCLC tissues than in adjacent normal lung tissues (LAC). Furthermore, the results from the Spearman correlation test showed a negative relationship between hsa-miR-125a-3p expression and pathological stage or lymph node metastasis and an inverse relationship between hsa-miR-125a-5p expression and pathological stage or lymph node metastasis. In vitro gain-of-function experiments indicated that hsa-miR-125a-3p and hsa-miR-125a-5p function in an opposing manner, suppressing or enhancing cell migration and invasion in A549 and SPC-A-1 cell lines, respectively. These opposing functions were further validated by suppression of hsa-miR-125a-3p and hsa-miR-125a-5p expression in loss-of-function experiments.

Conclusion

Hsa-miR-125a-3p and hsa-miR-125a-5p play distinct roles in regulation of invasive and metastatic capabilities of lung cancer cells, consistent with the opposing correlations between the expression of these miRNAs and lymph node metastasis in NSCLC. These results provide new insights into the roles of miR-125a family members in the development of NSCLC.

Role of carcinoma-associated fibroblasts and hypoxia in tumor progression

In recent years, a variety of experimental evidence has convincingly shown that progression of malignant tumors does not depend exclusively on cell-autonomous properties of the cancer cells, but can also be influenced by the tumor stroma. The concept that cancer cells are subjected to microenvironmental control has thus emerged as an important chapter in cancer biology. Recent findings have suggested an important role, in particular, for macrophages, endothelial cells, and cancer-associated fibroblasts (CAFs) in tumor growth and progression. Numerous lines of evidence indicate that the bone marrow is the source, at least in part, of these cells. This chapter summarizes our current knowledge of how bone marrow contributes to the tumor stroma, with particular emphasis on CAFs. The potential role of hypoxia in modulating the differentiation and activity of CAFs, and the therapeutical implications of targeting CAFs for anticancer therapy are discussed.

Epidermal Notch1 loss promotes skin tumorigenesis by impacting the stromal microenvironment

Notch1 is a proto-oncogene in several organs. In the skin, however, Notch1 deletion leads to tumor formation, suggesting that Notch1 is a "tumor suppressor" within this context. Here we demonstrate that, unlike classical tumor suppressors, Notch1 loss in epidermal keratinocytes promotes tumorigenesis non-cell autonomously by impairing skin-barrier integrity and creating a wound-like microenvironment in the skin. Using mice with a chimeric pattern of Notch1 deletion, we determined that Notch1-expressing keratinocytes in this microenvironment readily formed papillomas, showing that Notch1 was insufficient to suppress this tumor-promoting effect. Accordingly, loss of other Notch paralogues that impaired the skin barrier also predisposed Notch1-expressing skin to tumorigenesis, demonstrating that the tumor-promoting effect of Notch1 loss involves a crosstalk between barrier-defective epidermis and its stroma.

The lupane-type triterpene 30-oxo-calenduladiol is a CCR5 antagonist with anti-HIV-1 and anti-chemotactic activities

The existence of drug-resistant human immunodeficiency virus (HIV) viruses in patients receiving antiretroviral treatment urgently requires the characterization and development of new antiretroviral drugs designed to inhibit resistant viruses and to complement the existing antiretroviral strategies against AIDS. We assayed several natural or semi-synthetic lupane-type pentacyclic triterpenes in their ability to inhibit HIV-1 infection in permissive cells. We observed that the 30-oxo-calenduladiol triterpene, compound 1, specifically impaired R5-tropic HIV-1 envelope-mediated viral infection and cell fusion in permissive cells, without affecting X4-tropic virus. This lupane derivative competed for the binding of a specific anti-CCR5 monoclonal antibody or the natural CCL5 chemokine to the CCR5 viral coreceptor with high affinity. 30-oxo-calenduladiol seems not to interact with the CD4 antigen, the main HIV receptor, or the CXCR4 viral coreceptor. Our results suggest that compound 1 is a specific CCR5 antagonist, because it binds to the CCR5 receptor without triggering cell signaling or receptor internalization, and inhibits RANTES (regulated on activation normal T cell expressed and secreted)-mediated CCR5 internalization, intracellular calcium mobilization, and cell chemotaxis. Furthermore, compound 1 appeared not to interact with beta-chemokine receptors CCR1, CCR2b, CCR3, or CCR4. Thereby, the 30-oxo-calenduladiol-associated anti-HIV-1 activity against R5-tropic virus appears to rely on the selective occupancy of the CCR5 receptor to inhibit CCR5-mediated HIV-1 infection. Therefore, it is plausible that the chemical structure of 30-oxo-calenduladiol or other related dihydroxylated lupane-type triterpenes could represent a good model to develop more potent anti-HIV-1 molecules to inhibit viral infection by interfering with early fusion and entry steps in the HIV life cycle.

The metastatic niche: adapting the foreign soil

The 'seed and soil' hypothesis for metastasis sets forth the concept that a conducive microenvironment, or niche, is required for disseminating tumour cells to engraft distant sites. This Opinion presents emerging data that support this concept and outlines the potential mechanism and temporal sequence by which changes occur in tissues distant from the primary tumour. To enable improvements in the prognosis of advanced malignancy, early interventions that target both the disseminating seed and the metastatic soil are likely to be required.

MAVS-mediated apoptosis and its inhibition by viral proteins

Background

Host responses to viral infection include both immune activation and programmed cell death. The mitochondrial antiviral signaling adaptor, MAVS (IPS-1, VISA or Cardif) is critical for host defenses to viral infection by inducing type-1 interferons (IFN-I), however its role in virus-induced apoptotic responses has not been elucidated.

Principal Findings

We show that MAVS causes apoptosis independent of its function in initiating IFN-I production. MAVS-induced cell death requires mitochondrial localization, is caspase dependent, and displays hallmarks of apoptosis. Furthermore, MAVS^−/− fibroblasts are resistant to Sendai virus-induced apoptosis. A functional screen identifies the hepatitis C virus NS3/4A and the Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) nonstructural protein (NSP15) as inhibitors of MAVS-induced apoptosis, possibly as a method of immune evasion.

Significance

This study describes a novel role for MAVS in controlling viral infections through the induction of apoptosis, and identifies viral proteins which inhibit this host response.

Pulmonary fibrosis: pathogenesis, etiology and regulation

Pulmonary fibrosis and architectural remodeling of tissues can severely disrupt lung function, often with fatal consequences. The etiology of pulmonary fibrotic diseases is varied, with an array of triggers including allergens, chemicals, radiation and environmental particles. However, the cause of one of the most common pulmonary fibrotic conditions, idiopathic pulmonary fibrosis (IPF), is still unclear. This review examines common mechanisms of pulmonary wound-healing responses following lung injury, and highlights the pathogenesis of some of the most widespread pulmonary fibrotic diseases. A three phase model of wound repair is reviewed that includes; (1) injury; (2) inflammation; and (3) repair. In most pulmonary fibrotic conditions dysregulation at one or more of these phases has been reported. Chronic inflammation can lead to an imbalance in the production of chemokines, cytokines, growth factors, and disrupt cellular recruitment. These changes coupled with excessive pro-fibrotic IL-13 and/or TGFbeta1 production can turn a well-controlled healing response into a pathogenic fibrotic response. Endogenous regulatory mechanisms are discussed including novel areas of therapeutic intervention. Restoring homeostasis to these dysregulated healing responses, or simply neutralizing the key pro-fibrotic mediators may prevent or slow the progression of pulmonary fibrosis.

Chemokines in neuroectodermal cancers: the crucial growth signal from the soil

Although chemokines and their receptors were initially identified as regulators of cell trafficking during inflammation and immune response, they have emerged as crucial players in all stages of tumor development, primary growth, migration, angiogenesis, and establishment as metastases in distant target organs. Neuroectodermal tumors regroup neoplasms originating from the embryonic neural crest cells, which display clinical and biological similarities. These tumors are highly malignant and rapidly progressing diseases that disseminate to similar target organs such as bone marrow, bone, liver and lungs. There is increasing evidence that interaction of several chemokine receptors with corresponding chemokine ligands are implicated in the growth and invasive characteristics of these tumors. In this review we summarize the current knowledge on the role of CXCL12 chemokine and its CXCR4 and CXCR7 receptors in the progression and survival of neuroectodermal tumors, with particular emphasis on neuroblastoma, the most typical and enigmatic neuroectodermal childhood tumor.