Targeting the CCL2-CCR2 signaling axis in cancer metastasis

Tumor-associated macrophages in breast cancer: Innocent bystander or important player?

Tumor-associated macrophages (TAMs) are important tumor-promoting cells in the breast tumor microenvironment. Preclinically TAMs stimulate breast tumor progression, including tumor cell growth, invasion and metastasis. TAMs also induce resistance to multiple types of treatment in breast cancer models. The underlying mechanisms include: induction and maintenance of tumor-promoting phenotype in TAMs, inhibition of CD8+ T cell function, degradation of extracellular matrix, stimulation of angiogenesis and inhibition of phagocytosis. Several studies reported that high TAM infiltration of breast tumors is correlated with a worse patient prognosis. Based on these findings, macrophage-targeted treatment strategies have been developed and are currently being evaluated in clinical breast cancer trials. These strategies include: inhibition of macrophage recruitment, repolarization of TAMs to an antitumor phenotype, and enhancement of macrophage-mediated tumor cell killing or phagocytosis. This review summarizes the functional aspects of TAMs and the rationale and current evidence for TAMs as a therapeutic target in breast cancer.

MK2 Regulates Macrophage Chemokine Activity and Recruitment to Promote Colon Tumor Growth

A major risk factor for colon cancer growth and progression is chronic inflammation. We have shown that the MAPK-activated protein kinase 2 (MK2) pathway is critical for colon tumor growth in colitis-associated and spontaneous colon cancer models. This pathway is known to regulate expression of the tumor-promoting cytokines, IL-1, IL-6, and TNF-α. However, little is known about the ability of MK2 to regulate chemokine production. This is the first study to demonstrate this pathway also regulates the chemokines, MCP-1, Mip-1α, and Mip-2α (MMM). We show that these chemokines induce tumor cell growth and invasion in vitro and that MK2 inhibition suppresses tumor cell production of chemokines and reverses the resulting pro-tumorigenic effects. Addition of MMM to colon tumors in vivo significantly enhances tumor growth in control tumors and restores tumor growth in the presence of MK2 inhibition. We also demonstrate that MK2 signaling is critical for chemokine expression and macrophage influx to the colon tumor microenvironment. MK2 signaling in macrophages was essential for inflammatory cytokine/chemokine production, whereas MK2^−/− macrophages or MK2 inhibition suppressed cytokine expression. We show that addition of bone marrow-derived macrophages to the tumor microenvironment enhances tumor growth in control tumors and restores tumor growth in tumors treated with MK2 inhibitors, while addition of MK2^−/− macrophages had no effect. This is the first study to demonstrate the critical role of the MK2 pathway in chemokine production, macrophage influx, macrophage function, and tumor growth.

Combining radiation therapy and cancer immune therapies: From preclinical findings to clinical applications

Besides its direct cytotoxic effect on the tumor cells, radiation therapy is also able to elicit an immune-mediated systemic anti-tumor response, resulting in tumor regression in irradiated sites but also within distant out of field secondary lesions and providing a long-term anti-tumor response. It is now clear that associating ionizing radiation with immune therapies can enhance radio-induced anti-tumor immune responses. Over the last decade, such a combination aroused considerable interest among the scientific community, with many preclinical models and clinical trials, using many types of immune therapies and radiation regimens. In this article, we summarize the main mechanisms underlying radio-induced anti-tumor responses. We will then present an extended overview of the recent preclinical and clinical research built on this background of combined radiation and immune therapy, shedding light on what we know so far about such a promising strategy.

MicroRNA-135a-3p is downregulated and serves as a tumour suppressor in ovarian cancer by targeting CCR2

MicroRNAs have been demonstrated to play a crucial role in the development of ovarian cancer. Many studies prove that forms of miR-135a, including miR-135a-5p and miR-135a-3p, serve as tumour suppressors in multiple cancers. Nevertheless, the precise function of miR-135a-3p and the molecular mechanisms underlying the involvement of miR-135a-3p in ovarian carcinoma cell growth and metastasis remain largely unknown. Herein, we report that miR-135a-3p expression was significantly downregulated in ovarian carcinoma tissues compared with corresponding adjacent non-tumour tissues. Ectopic miR-135a-3p expression inhibited ovarian carcinoma cell proliferation, migration and invasion in vitro. Additionally, the overexpression of miR-135a-3p inhibited epithelial-mesenchymal transition (EMT) in ovarian cancer cells. A luciferase reporter assay confirmed that the C-C chemokine receptor type 2 (CCR2) gene was the target of miR-135a-3p. In addition, CCR2 depletion mimicked the inhibitory effects of miR-135a-3p on ovarian cancer cells in vitro. Rescue experiments using CCR2 overexpression further verified that CCR2 was a functional target of miR-135a-3p. Xenograft model assays demonstrated that miR-135a-3p functions as an anti-oncogene by targeting CCR2 in vivo. Taken together, these data prove that miR-135a-3p serves as a tumour suppressor gene in ovarian cancer by regulating CCR2.

Impact of chemotactic factors and receptors on the cancer immune infiltrate: a bioinformatics study revealing homogeneity and heterogeneity among patient cohorts

Multiple soluble factors including proteins (in particular chemokines), non-proteinaceous factors released by dead cells, as well as receptors for such factors (in particular chemokine receptors, formyl peptide receptors and purinergic receptors), influence the recruitment of distinct cell subsets into the tumor microenvironment. We performed an extensive bioinformatic analysis on tumor specimens from 5953 cancer patients to correlate the mRNA expression levels of chemotactic factors/receptors with the density of immune cell types infiltrating the malignant lesions. This meta-analysis, which included specimens from breast, colorectal, lung, ovary and head and neck carcinomas as well as melanomas, revealed that a subset of chemotactic factors/receptors exhibited a positive and reproducible correlation with several infiltrating cell types across various solid cancers, revealing a universal pattern of association. Hence, this meta-analysis distinguishes between homogeneous associations that occur across different cancer types and heterogeneous correlations, that are specific of one organ. Importantly, in four out of five breast cancer cohorts for which clinical data were available, the levels of expression of chemotactic factors/receptors that exhibited universal (rather than organ-specific) positive correlations with the immune infiltrate had a positive impact on the response to neoadjuvant chemotherapy. These results support the notion that general (rather than organ-specific) rules governing the recruitment of immune cells into the tumor bed are particularly important in determining local immunosurveillance and response to therapy.

Recruitment of CCR2+ tumor associated macrophage to sites of liver metastasis confers a poor prognosis in human colorectal cancer

The tumor microenvironment (TME) represents a significant barrier to creating effective therapies for metastatic colorectal cancer (mCRC). In several malignancies, bone marrow derived CCR2+ inflammatory monocytes (IM) are recruited to the TME by neoplastic cells, where they become immunosuppressive tumor associated macrophages (TAM). Here we report that mCRC expression of the chemokine CCL2 facilitates recruitment of CCR2+ IM from the bone marrow to the peripheral blood. Immune monitoring of circulating monocytes in patients with mCRC found this influx was a prognostic biomarker and correlated with worse clinical outcomes. At the metastatic site, mCRC liver tumors were heavily infiltrated by TAM, which displayed a robust ability to dampen endogenous anti-tumor lymphocyte activity. Using a murine model of mCRC that recapitulates these findings from human disease, we show that targeting CCR2 reduces TAM accumulation in liver metastasis and restores anti-tumor immunity. Additional quantitative analysis of hepatic metastatic tumor burden and treatment efficacy found that administration of a small molecule CCR2 inhibitor (CCR2i) improves chemotherapeutic responses and increases overall survival in mice with mCRC liver tumors. Our study suggests that targeting the CCL2/CCR2 chemokine axis decreases TAM at the metastatic site, disrupting the immunosuppressive TME and rendering mCRC susceptible to anti-tumor T-cell responses.

Interleukin-1 Beta-A Friend or Foe in Malignancies?

Interleukin-1 beta (IL-1β) is induced by inflammatory signals in a broad number of immune cell types. IL-1β (and IL-18) are the only cytokines which are processed by caspase-1 after inflammasome-mediated activation. This review aims to summarize current knowledge about parameters of regulation of IL-1β expression and its multi-facetted role in pathophysiological conditions. IL-1 signaling activates innate immune cells including antigen presenting cells, and drives polarization of CD4+ T cells towards T helper type (Th) 1 and Th17 cells. Therefore, IL-1β has been attributed a largely beneficial role in resolving acute inflammations, and by initiating adaptive anti-tumor responses. However, IL-1β generated in the course of chronic inflammation supports tumor development. Furthermore, IL-1β generated within the tumor microenvironment predominantly by tumor-infiltrating macrophages promotes tumor growth and metastasis via different mechanisms. These include the expression of IL-1 targets which promote neoangiogenesis and of soluble mediators in cancer-associated fibroblasts that evoke antiapoptotic signaling in tumor cells. Moreover, IL-1 promotes the propagation of myeloid-derived suppressor cells. Using genetic mouse models as well as agents for pharmacological inhibition of IL-1 signaling therapeutically applied for treatment of IL-1 associated autoimmune diseases indicate that IL-1β is a driver of tumor induction and development.

The regulation and importance of monocyte chemoattractant protein-1

PURPOSE OF REVIEW

Monocyte chemoattractant protein (MCP)-1, a chemokine regulating monocyte chemotaxis and T-lymphocyte differentiation by binding to the CC chemokine receptor 2 (CCR2), plays a crucial role in the pathogenesis of inflammatory diseases, atherosclerosis and cancer. This review summarizes the current knowledge on the regulation and importance of the MCP-1/CCR2 axis, focusing on the therapeutic potential of its inhibition.

RECENT FINDINGS

Differential modulation of MCP-1 and CCR2 lead to downstream activation pathways, pathogenetic to differing disease conditions characterized by dysregulated monocyte/macrophage tissue recruitment. Pharmacological targeting of the MCP-1/CCR2 axis has led to selective MCP-1/CCR2 antagonists that have now entered phase I/II clinical trials for the treatment of inflammatory diseases, atherosclerosis and cancer. The pleiotropic nonselective MCP-1/CCR2 inhibition by current pharmacological agents is thought to contribute to their anti-inflammatory and antiatherosclerotic effects that is also seen for nutraceutical compounds such as curcumin.

SUMMARY

MCP-1 has a critical role in regulating chemotaxis both in health and disease, with increasing interest in its pharmacological inhibition. However, the therapeutic efficacy and safety of targeting the MCP-1/CCR2 axis is still in evolution.

Reactive astrocytic S1P3 signaling modulates the blood-tumor barrier in brain metastases

Brain metastases are devastating complications of cancer. The blood-brain barrier (BBB), which protects the normal brain, morphs into an inadequately characterized blood-tumor barrier (BTB) when brain metastases form, and is surrounded by a neuroinflammatory response. These structures contribute to poor therapeutic efficacy by limiting drug uptake. Here, we report that experimental breast cancer brain metastases of low- and high permeability to a dextran dye exhibit distinct microenvironmental gene expression patterns. Astrocytic sphingosine-1 phosphate receptor 3 (S1P3) is upregulated in the neuroinflammatory response of the highly permeable lesions, and is expressed in patients' brain metastases. S1P3 inhibition functionally tightens the BTB in vitro and in vivo. S1P3 mediates its effects on BTB permeability through astrocytic secretion of IL-6 and CCL2, which relaxes endothelial cell adhesion. Tumor cell overexpression of S1P3 mimics this pathway, enhancing IL-6 and CCL-2 production and elevating BTB permeability. In conclusion, neuroinflammatory astrocytic S1P3 modulates BTB permeability.

Modulating Macrophage Polarization through CCR2 Inhibition and Multivalent Engagement

Excessive or prolonged recruitment of inflammatory monocytes to damaged tissue can significantly worsen patient outcomes. Monocytes migrate to sites of tissue inflammation in response to high local concentrations of CCL2, a chemokine that binds to and signals through the CCR2 receptor. While the role of CCR2 in cellular migration is well studied, it is unclear how CCR2 inhibition affects macrophage polarization and if multivalency can increase downstream signaling effects. Using affinity selection with a phage library, we identified a novel single-chain variable fragment (scFv) (58C) that binds specifically and with high affinity to the N-terminal domain of CCR2 ( KD = 59.8 nM). The newly identified 58C-scFv bound to native CCR2 expressed on macrophages and MDA-MB-231 cells, inhibited migration, and induced a pro-inflammatory M1-phenotype in macrophages. The M1/M2 macrophage phenotype ratio for monomeric 58C-scFv was significantly increased over the negative control by 1.0 × 104-fold (iNOS/Arg-1), 5.1 × 104-fold (iNOS/Mgl2), 3.4 × 105-fold (IL-6/Arg-1), and 1.7 × 106-fold (IL-6/Mgl2). The multivalent display of 58C-scFv on liposomes further reduced migration of both cell types by 25-40% and enhanced M1 polarization by 200% over monomeric 58C-scFv. These studies demonstrate that CCR2 inhibition polarizes macrophages toward an inflammatory M1 phenotype, and that multivalent engagement of CCR2 increases the effects of 58C-scFv on polarization and migration. These data provide important insights into the role of multivalency in modulating binding, downstream signaling, and cellular fate.

Discovery and synthesis of 6,7,8,9-tetrahydro-5H-pyrido[4,3-c]azepin-5-one-based novel chemotype CCR2 antagonists via scaffold hopping strategy

The chemokine CC receptor subtype 2 (CCR2) has attracted intensive interest for drug development in diverse therapeutic areas, including chronic inflammatory diseases, diabetes, neuropathic pain, atherogenesis and cancer. By employing a cut-and-sew scaffold hopping strategy, we identified an active scaffold of 3,4-dihydro-2,6-naphthyridin-1(2H)-one as the central pharmacophore to derive novel CCR2 antagonists. Systematic structure-activity relationship study with respect to the ring size and the substitution on the naphthyridinone ring gave birth to 1-arylamino-6-alkylheterocycle-6,7,8,9-tetrahydro-5H-pyrido[4,3-c]azepin-5-ones as a brand new chemotype of CCR2 antagonists with nanomolar inhibitory activity. The best antagonism activity in this series was exemplified by compound 13a, which combined the optimal substitutions of 3,4-dichlorophenylamino at C-1 and 3-(4-(N-methylmethylsulfonamido)piperidin-1-yl)propyl at N-6 position, leading to an IC₅₀ value of 61 nM and 10-fold selectivity for CCR2 over CCR5. Efficient and general synthesis was established to construct the innovative core structure and derive the compound collections. This is the first report on our designed 6,7,8,9-tetrahydro-5H-pyrido[4,3-c]azepin-5-one as novel CCR2 antagonist scaffold and its synthesis.

Upregulation of the Chemokine Receptor CCR2B in Epstein‒Barr Virus-Positive Burkitt Lymphoma Cell Lines with the Latency III Program

CCR2 is the cognate receptor to the chemokine CCL2. CCR2–CCL2 signaling mediates cancer progression and metastasis dissemination. However, the role of CCR2–CCL2 signaling in pathogenesis of B-cell malignancies is not clear. Previously, we showed that CCR2B was upregulated in ex vivo peripheral blood B cells upon Epstein‒Barr virus (EBV) infection and in established lymphoblastoid cell lines with the EBV latency III program. EBV latency III is associated with B-cell lymphomas in immunosuppressed patients. The majority of EBV-positive Burkitt lymphoma (BL) tumors are characterized by latency I, but the BL cell lines drift towards latency III during in vitro culture. In this study, the CCR2A and CCR2B expression was assessed in the isogenic EBV-positive BL cell lines with latency I and III using RT-PCR, immunoblotting, and immunostaining analyses. We found that CCR2B is upregulated in the EBV-positive BL cells with latency III. Consequently, we detected the migration of latency III cells toward CCL2. Notably, the G190A mutation, corresponding to SNP CCR2-V64I, was found in one latency III cell line with a reduced migratory response to CCL2. The upregulation of CCR2B may contribute to the enhanced migration of malignant B cells into CCL2-rich compartments.

Host chemokine signature as a biomarker for the detection of pre-cancerous cervical lesions

Background

The ability to distinguish which hrHPV infections predispose to significant disease is ever more pressing as a result of the increasing move to hrHPV testing for primary cervical screening. A risk-stratifier or “triage” of infection should ideally be objective and suitable for automation given the scale of screening.

Results

CCL2, CCL3, CCL4, CXCL1, CXCL8 and CXCL12 emerged as the strongest, candidate biomarkers to detect underlying disease [cervical intraepithelial neoplasia grade 2 or worse (CIN2+)]. For CIN2+, CCL2 had the highest area under the curve (AUC) of 0.722 with a specificity of 82%. A combined biomarker panel of six chemokines CCL2, CCL3, CCL4, CXCL1, CXCL8, and CXCL12 provides a sensitivity of 71% and specificity of 67%.

Conclusion

The present work demonstrates that the levels of five chemokine-proteins are indicative of underlying disease. We demonstrate technical feasibility and promising clinical performance of a chemokine-based biomarker panel, equivalent to that of other triage options. Further assessment in longitudinal series is now warranted.

Methods

A panel of 31 chemokines were investigated for expression in routinely taken archived and prospective cervical liquid based cytology (LBC) samples using Human Chemokine Proteomic Array kit. Nine chemokines were further validated using Procartaplex assay on the Luminex platform.

Targeting Accessories to the Crime: Nanoparticle Nucleic Acid Delivery to the Tumor Microenvironment

Nucleic acid delivery for cancer holds extraordinary promise. Increasing expression of tumor suppressor genes or inhibition of oncogenes in cancer cells has important therapeutic potential. However, several barriers impair progress in cancer gene delivery. These include effective delivery to cancer cells and relevant intracellular compartments. Although viral gene delivery can be effective, it has the disadvantages of being immuno-stimulatory, potentially mutagenic and lacking temporal control. Various nanoparticle (NP) platforms have been developed to overcome nucleic acid delivery hurdles, but several challenges still exist. One such challenge has been the accumulation of NPs in non-cancer cells within the tumor microenvironment (TME) as well as the circulation. While uptake by these cancer-associated cells is considered to be an off-target effect in some contexts, several strategies have now emerged to utilize NP-mediated gene delivery to intentionally alter the TME. For example, the similarity of NPs in shape and size to pathogens promotes uptake by antigen presenting cells, which can be used to increase immune stimulation and promote tumor killing by T-lymphocytes. In the era of immunotherapy, boosting the ability of the immune system to eliminate cancer cells has proven to be an exciting new area in cancer nanotechnology. Given the importance of cancer-associated cells in tumor growth and metastasis, targeting these cells in the TME opens up new therapeutic applications for NPs. This review will cover evidence for non-cancer cell accumulation of NPs in animal models and patients, summarize characteristics that promote NP delivery to different cell types, and describe several therapeutic strategies for gene modification within the TME.

Role of Macrophages in Brain Tumor Growth and Progression

The role of macrophages in the growth and the progression of tumors has been extensively studied in recent years. A large body of data demonstrates that macrophage polarization plays an essential role in the growth and progression of brain tumors, such as gliomas, meningiomas, and medulloblastomas. The brain neoplasm cells have the ability to influence the polarization state of the tumor associated macrophages. In turn, innate immunity cells have a decisive role through regulation of the acquired immune response, but also through humoral cross-talking with cancer cells in the tumor microenvironment. Neoangiogenesis, which is an essential element in glial tumor progression, is even regulated by the tumor associated macrophages, whose activity is linked to other factors, such as hypoxia. In addition, macrophages play a decisive role in establishing the entry into the bloodstream of cancer cells. As is well known, the latter phenomenon is also present in brain tumors, even if they only rarely metastasize. Looking ahead in the future, we can imagine that characterizing the relationships between tumor and tumor associated macrophage, as well as the study of circulating tumor cells, could give us useful tools in prognostic evaluation and therapy. More generally, the study of innate immunity in brain tumors can boost the development of new forms of immunotherapy.

Tumor-associated macrophages in human breast cancer produce new monocyte attracting and pro-angiogenic factor YKL-39 indicative for increased metastasis after neoadjuvant chemotherapy

In breast cancer, the tumor microenvironment plays a critical role in the tumor progression and responses to therapy. Tumor-associated macrophages (TAMs) are major innate immune cells in tumor microenvironment that regulate intratumoral immunity and angiogenesis by secretion of cytokines, growth factors as well as chitinase-like proteins (CLPs), that combine properties of cytokines and growth factors. YKL-39 is a chitinase-like protein found in human and absent in rodents, and its expression in TAMs and role in breast cancer progression was not studied to date. Here for the first time we demonstrate that YKL-39 is expressed on TAMs, predominantly positive for stabilin-1, but not by malignant cells or other stromal cells in human breast cancer. TGF-beta in combination with IL-4, but not IL-4 alone was responsible of the stimulation of the production of YKL-39 in human primary macrophages. Mechanistically, stabilin-1 directly interacted with YKL-39 and acted as sorting receptor for targeting YKL-39 into the secretory pathway. Functionally, purified YKL-39 acted as a strong chemotactic factor for primary human monocytes, and induced angiogenesis in vitro. Elevated levels of YKL-39 expression in tumors after neoadjuvant chemotherapy (NAC) were predictive for increased risk of distant metastasis and for poor response to NAC in patients with nonspecific invasive breast carcinoma. Our findings suggest YKL-39 as a novel therapeutic target, and blocking of its activity can be combined with NAC in order to reduce the risk of metastasis in breast cancer patients.

Monocyte chemoattractant protein 1 and fractalkine play opposite roles in angiogenesis via recruitment of different macrophage subtypes

AIM

To explore the interaction between macrophages and chemokines [monocyte chemoattractant protein 1 (MCP-1/CCL2) and fractalkine/CX3CL1] and the effects of their interaction on neovascularization.

METHODS

Human peripheral blood mononuclear cells, donated by healthy volunteers, were separated and cultured in RPMI-1640 medium containing 10% fetal bovine serum, then induced into macrophages by stimulation with 30 µg/L granulocyte macrophage-colony stimulating factor (GM-CSF). The expression of CCR2 and/or CX3CR1 in the macrophages was examined using flow cytometry. Macrophages were then stimulated with recombinant human CCL2 (rh-CCL2) or recombinant human CX3CL1 (rh-CX3CL1). The expression of angiogenesis-related genes, including VEGF-A, THBS-1 and ADAMTS-1 were examined using real-time quantitative polymerase chain reaction (PCR). Supernatants from stimulated macrophages were used in an assay of human retinal endothelial cell (HREC) proliferation. Finally, stimulated macrophages were co-cultured with HREC in a migration assay.

RESULTS

The expression rate of CCR2 in macrophages stimulated by GM-CSF was 42%±1.9%. The expression rate of CX3CR1 was 71%±3.3%. Compared with vehicle-treated groups, gene expression of VEGF-A in the macrophages was greater in 150 mg/L CCL2-treated groups (P<0.05), while expression of THBS-1 and ADAMTS-1 was significantly lower (P<0.05). By contrast, compared with vehicle-treated groups, expression of VEGF-A in 150 mg/L CX3CL1-treated groups was significantly lower (P<0.05), while expression of THBS-1 and ADAMTS-1 was greater (P<0.05). Supernatants from CCL2 treated macrophages promoted proliferation of HREC (P<0.05), while supernatants from CX3CL1-treated macrophages inhibited the proliferation of HREC (P<0.05). HREC migration increased when co-cultured with CCL2-treated macrophages, but decreased with CX3CL1-treated macrophages (P<0.05).

CONCLUSION

CCL2 and CX3CL1 exert different effects in regulation of macrophage in expression of angiogenesis-related factors, including VEGF-A, THBS-1 and ADAMTS-1. Our findings suggest that CCL2 and CX3CL1 may be candidate proteins for further exploration of novel targets for treatment of ocular neovascularization.

A core matrisome gene signature predicts cancer outcome

BACKGROUND

Accumulating evidence implicates the tumour stroma as an important determinant of cancer progression but the protein constituents relevant for this effect are unknown. Here we utilised a bioinformatics approach to identify an extracellular matrix (ECM) gene signature overexpressed in multiple cancer types and strongly predictive of adverse outcome.

METHODS

Gene expression levels in cancers were determined using Oncomine. Geneset enrichment analysis was performed using the Broad Institute desktop application. Survival analysis was performed using KM plotter. Survival data were generated from publically available genesets.

RESULTS

We analysed ECM genes significantly upregulated across a large cohort of patients with ovarian, lung, gastric and colon cancers and defined a signature of nine commonly upregulated genes. Each of these nine genes was considerably overexpressed in all the cancers studied, and cumulatively, their expression was associated with poor prognosis across all data sets. Further, the gene signature expression was associated with enrichment of genes governing processes linked to poor prognosis, such as EMT, angiogenesis, hypoxia, and inflammation.

CONCLUSIONS

Here we identify a nine-gene ECM signature, which strongly predicts outcome across multiple cancer types and can be used for prognostication after validation in prospective cancer cohorts.

CCL2/CCR2 axis is associated with postoperative survival and recurrence of patients with non-metastatic clear-cell renal cell carcinoma

PURPOSE

Chemokine (C-Cmotif) ligand 2 (CCL2) is a major chemokine that recruit monocytes and macrophages to the sites of inflammation. Recent researches have clarified that overexpression of CCL2 is associated with unfavorable prognosis in various cancer types. In this study, we aim to determine the prognostic value of CCL2 expression as well as its receptor C-C motif receptor type 2 (CCR2) in patients with non-metastatic clear cell renal cell carcinoma (ccRCC) after surgery.

RESULTS

Both high CCL2 and CCR2 expression were remarkably correlated with shortened survival time (P < 0.001 and P < 0.001, respectively) and increased risk of recurrence (P = 0.001 and P = 0.003, respectively). The combination of CCL2 and CCR2 expression (CCL2/CCR2 signature) could offer a better prognostic stratification. Furthermore, multivariate analyses identified CCL2/CCR2 signature as an independent risk factor for overall survival (OS) and recurrence-free survival (RFS) (P = 0.007 and P = 0.043, respectively). The incorporation of CCL2/CCR2 signature would refine individual risk stratification and predictive accuracy of the well-established models.

MATERIALS AND METHODS

We retrospectively examined the intratumoral expression of CCL2 and CCR2 by immunohistochemical staining in 268 histologically proven non-metastatic ccRCC patients receiving surgery in a single institution between 2001 and 2004. Kaplan-Meier analysis and Cox regression were applied to determine the prognostic value of CCL2 and CCR2 expression. Concordance index was calculated to compare predictive accuracy of the established models.

CONCLUSIONS

Combined CCL2 and CCR2 expression emerges as an independent prognostic factor for non-metastatic ccRCC patients after surgical treatment.

Macrophages: Key orchestrators of a tumor microenvironment defined by therapeutic resistance

Macrophages have emerged as promising therapeutic targets in cancer. Within tumor tissue, macrophages foster tumor development, invasion, and metastasis. As the phenotype of macrophages is inherently pliable and dependent on cues received from the surrounding microenvironment, macrophages co-evolve with malignant and other non-malignant cells during cancer progression. In doing so, they establish a microenvironment that is therapeutically resistant and thwarts the productivity of T cell immunosuveillance. Strategies designed to deplete, inhibit, or redirect macrophages with anti-tumor activity are being explored to reverse the pro-tumor properties of macrophages that are commonly observed in cancer. In this review, we discuss our current understanding of the mechanisms that regulate macrophage recruitment to tumors, their impact on the tumor microenvironment, and their promise as therapeutic targets for improving the efficacy of cytotoxic- and immune-based therapies.

Clinical evaluation of macrophages in cancer: role in treatment, modulation and challenges

The focus of immunotherapeutics has been placed firmly on anti-tumour T cell responses. Significant progress has been made in the treatment of both local and systemic malignancies, but low response rates and rising toxicities are limiting this approach. Advancements in the understanding of tumour immunology are opening up a new range of therapeutic targets, including immunosuppressive factors in the tumour microenvironment. Macrophages are a heterogeneous group of cells that have roles in innate and adaptive immunity and tissue repair, but become co-opted by tumours to support tumour growth, survival, metastasis and immunosuppression. Macrophages also support tumour resistance to conventional therapy. In preclinical models, interference with macrophage migration, macrophage depletion and macrophage re-education have all been shown to reduce tumour growth and support anti-tumour immune responses. Here we discuss the role of macrophages in prognosis and sensitivity to therapy, while examining the significant progress which has been made in modulating the behaviour of these cells in cancer patients.

Chronic psychological stress promotes lung metastatic colonization of circulating breast cancer cells by decorating a pre-metastatic niche through activating β-adrenergic signaling

Numerous studies have indicated that primary tumors induce the formation of a pre-metastatic niche in distant organs by secreting tumor-derived factors. The present study shows that pre-exposure to chronic stress enhanced lung colonization efficiency by circulating tumor cells, suggesting that chronic stress critically influences pre-metastatic lungs before the arrival of disseminated tumor cells. Ablation of the sympathetic nerve function by 6-OHDA or blockage of the β-adrenergic signaling by propranolol remarkably suppressed stress-induced lung metastasis. Depletion of circulating monocytes or lung macrophages strongly abolished stress-induced lung seeding by tumor cells, whereas treatment of mice with the β-adrenergic agonist isoproterenol (ISO) during the pre-metastatic phase promoted the infiltration of macrophages to the lung. Meanwhile, the numbers of monocytes in peripheral blood, spleen, and bone marrow were remarkably increased in response to ISO stimulation. These data indicate that the β-adrenergic signaling promotes lung metastatic colonization by tumor cells through increased output of monocytes in the pre-metastatic phase and infiltration of macrophages into the pre-metastatic lung. Mechanistic studies revealed that ISO stimulation upregulated the expression of CCL2 in pulmonary stromal cells and CCR2 in monocytes/macrophages, leading to the recruitment and infiltration of macrophages into the pre-metastatic lung. By inducing a response of monocytes/macrophages driven by the CCL2/CCR2 axis, stress-related catecholamine may act as a crucial factor in regulating the pre-metastatic niche for and lung colonization by tumor cells. Our data demonstrate that disturbance of host macro-environmental homeostasis has an influence on future metastatic organs. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Chemokine Signaling Facilitates Early-Stage Breast Cancer Survival and Invasion through Fibroblast-Dependent Mechanisms

Ductal carcinoma in situ (DCIS) is the most common form of breast cancer, with 50,000 cases diagnosed every year in the United States. Overtreatment and undertreatment remain significant clinical challenges in patient care. Identifying key mechanisms associated with DCIS progression could uncover new biomarkers to better predict patient prognosis and improve guided treatment. Chemokines are small soluble molecules that regulate cellular homing through molecular gradients. CCL2-mediated recruitment of CCR2⁺ macrophages are a well-established mechanism for metastatic progression. Although the CCL2/CCR2 pathway is a therapeutic target of interest, little is known about the role of CCR2 expression in breast cancer. Here, using a mammary intraductal injection (MIND) model to mimic DCIS formation, the role of CCR2 was explored in minimally invasive SUM225 and highly invasive DCIS.com breast cancer cells. CCR2 overexpression increased SUM225 breast cancer survival and invasion associated with accumulation of CCL2 expressing fibroblasts. CCR2-deficient DCIS.com breast cancer cells formed fewer invasive lesions with fewer CCL2⁺ fibroblasts. Cografting CCL2-deficient fibroblasts with DCIS.com breast cancer cells in the subrenal capsule model inhibited tumor invasion and survival associated with decreased expression of aldehyde dehydrogenase (ALDH1), a proinvasive factor, and decreased expression of HTRA2, a proapoptotic serine protease. Through data mining analysis, high expression of CCR2 and ALDH1 and low HTRA2 expression were correlated with poor prognosis of breast cancer patients.Implications: This study demonstrates that CCR2 overexpression in breast cancer drives early-stage breast cancer progression through stromal-dependent expression of CCL2 with important insight into prognosis and treatment of DCIS. Mol Cancer Res; 16(2); 296-308. ©2017 AACR.

CCL2/CCR2 axis induces hepatocellular carcinoma invasion and epithelial-mesenchymal transition in vitro through activation of the Hedgehog pathway

Chemokine (C-C motif) ligand 2 (CCL2) has been shown to play an important role in the regulation of tumor cell growth, metastasis and host immune response. CCL2 preferentially binds to the C-C chemokine receptor type 2 (CCR2), which is expressed in various tissues. However, the role of the CCL2/CCR2 axis in hepatocellular carcinoma (HCC) invasion and its molecular mechanisms remain unclear. The aim of this study was to elucidate this issue. The human HCC cell line MHCC-97H was treated with CCL2. Cyclopamine, a smoothened (SMO) antagonist, was used to inhibit SMO activity. CCR2 siRNA and Gli-1 siRNA were used to inhibit CCR2 and Gli-1 expression respectively. The effect of CCL2 and Hedgehog (Hh) signaling on cancer cell epithelial-mesenchymal transition (EMT) and invasion was evaluated by quantitative real-time PCR analysis, western blotting and Transwell invasion assay. Our results revealed that CCL2 induced HCC cell invasion and EMT. This effect was accompanied by the activation of Hh signaling, the upregulation of Snail and vimentin and the reduction of E-cadherin. Notably, prior silencing of CCR2 with siRNA abolished CCL2-induced Hh signaling activation, Snail and vimentin upregulation, E-cadherin reduction, as well as HCC cell invasion and EMT. Furthermore, pretreatment with cyclopamine or predepletion of Gli-1 by siRNA also eliminated the changes of Snail, vimentin and E-cadherin, and HCC invasion and EMT caused by CCL2. Collectively, our results revealed that the link between the CCL2/CCR2 axis and the Hh pathway plays an important role in HCC progression. Therefore, the CCL2/CCR2 axis may represent a promising therapeutic target to prevent HCC progression.

A drug development perspective on targeting tumor-associated myeloid cells

Despite decades of research, cancer remains a devastating disease and new treatment options are needed. Today cancer is acknowledged as a multifactorial disease not only comprising of aberrant tumor cells but also the associated stroma including tumor vasculature, fibrotic plaques, and immune cells that interact in a complex heterotypic interplay. Myeloid cells represent one of the most abundant immune cell population within the tumor stroma and are equipped with a broad functional repertoire that promotes tumor growth by suppressing cytotoxic T cell activity, stimulating neoangiogenesis and tissue remodeling. Therefore, myeloid cells have become an attractive target for pharmacological intervention. In this review, we summarize the pharmacological approaches to therapeutically target tumor-associated myeloid cells with a focus on advanced programs that are clinically evaluated. In addition, for each therapeutic strategy, the preclinical rationale as well as advantages and challenges from a drug development perspective are discussed.

The CCR2 3'UTR functions as a competing endogenous RNA to inhibit breast cancer metastasis

Diverse RNA transcripts acting as competing endogenous RNAs (ceRNAs) can co-regulate each other's expression by competing for shared microRNAs. CCR2 protein, the receptor for CCL2, is implicated in cancer progression. However, we found that a higher CCR2 mRNA level is remarkably associated with prolonged survival of breast cancer patients. These conflicting results prompted us to study the non-coding function of CCR2 mRNA. We found that the CCR2 3' untranslated region (UTR) inhibited MDA-MB-231 and MCF-7 cell metastasis by repressing epithelial-mesenchymal transition (EMT) in vitro, and suppressed breast cancer metastasis in vivo Mechanistically, the CCR2 3'UTR modulated the expression of the RhoGAP protein STARD13 via acting as a STARD13 ceRNA in a microRNA-dependent and protein coding-independent manner. The CCR2 3'UTR blocked the activation of RhoA-ROCK1 pathway, which is the downstream effector of STARD13, and thus decreased the phosphorylation level of myosin light chain 2 (MLC2) and formation of F-actin. Additionally, the function of the CCR2 3'UTR was dependent on STARD13 expression. In conclusion, our results confirmed that the CCR2 3'UTR acts as a metastasis suppressor by acting as a ceRNA for STARD13 and thus inhibiting RhoA-ROCK1-MLC-F-actin pathway in breast cancer cells.This article has an associated First Person interview with the first author of the paper.

Protein Mimetic and Anticancer Properties of Monocyte-Targeting Peptide Amphiphile Micelles

Monocyte chemoattractant protein-1 (MCP-1) stimulates the migration of monocytes to inflammatory sites, leading to the progression of many diseases. Recently, we described a monocyte-targeting peptide amphiphile micelle (MCP-1 PAM) incorporated with the chemokine receptor CCR2 binding motif of MCP-1, which has a high affinity for monocytes in atherosclerotic plaques. We further report here the biomimetic components of MCP-1 PAMs and the influence of the nanoparticle upon binding to monocytes. We report that MCP-1 PAMs have enhanced secondary structure compared to the MCP-1 peptide. As a result, MCP-1 PAMs displayed improved binding and chemoattractant properties to monocytes, which upregulated the inflammatory signaling pathways responsible for monocyte migration. Interestingly, when MCP-1 PAMs were incubated in the presence of prostate cancer cells in vitro, the particle displayed anticancer efficacy by reducing CCR2 expression. Given that monocytes play an important role in tumor cell migration and invasion, our results demonstrate that PAMs can improve the native biofunctional properties of the peptide and may be used as an effective inhibitor to prevent chemokine-receptor interactions that promote disease progression.

Genomic Landscape of Atypical Adenomatous Hyperplasia Reveals Divergent Modes to Lung Adenocarcinoma

There is a dearth of knowledge about the pathogenesis of premalignant lung lesions, especially for atypical adenomatous hyperplasia (AAH), the only known precursor for the major lung cancer subtype adenocarcinoma (LUAD). In this study, we performed deep DNA and RNA sequencing analyses of a set of AAH, LUAD, and normal tissues. Somatic BRAF variants were found in AAHs from 5 of 22 (23%) patients, 4 of 5 of whom had matched LUAD with driver EGFR mutations. KRAS mutations were present in AAHs from 4 of 22 (18%) of patients. KRAS mutations in AAH were only found in ever-smokers and were exclusive to BRAF-mutant cases. Integrative analysis revealed profiles expressed in KRAS-mutant cases (UBE2C, REL) and BRAF-mutant cases (MAX) of AAH, or common to both sets of cases (suppressed AXL). Gene sets associated with suppressed antitumor (Th1; IL12A, GZMB) and elevated protumor (CCR2, CTLA-4) immune signaling were enriched in AAH development and progression. Our results reveal potentially divergent BRAF or KRAS pathways in AAH as well as immune dysregulation in the pathogenesis of this premalignant lung lesion. Cancer Res; 77(22); 6119-30. ©2017 AACR.

Applying nanomedicine in maladaptive inflammation and angiogenesis

Inflammation and angiogenesis drive the development and progression of multiple devastating diseases such as atherosclerosis, cancer, rheumatoid arthritis, and inflammatory bowel disease. Though these diseases have very different phenotypic consequences, they possess several common pathophysiological features in which monocyte recruitment, macrophage polarization, and enhanced vascular permeability play critical roles. Thus, developing rational targeting strategies tailored to the different stages of the journey of monocytes, from bone marrow to local lesions, and their extravasation from the vasculature in diseased tissues will advance nanomedicine. The integration of in vivo imaging uniquely allows studying nanoparticle kinetics, accumulation, clearance, and biological activity, at levels ranging from subcellular to an entire organism, and will shed light on the fate of intravenously administered nanomedicines. We anticipate that convergence of nanomedicines, biomedical engineering, and life sciences will help to advance clinically relevant therapeutics and diagnostic agents for patients with chronic inflammatory diseases.

Beyond the M-CSF receptor - novel therapeutic targets in tumor-associated macrophages

Tumor-associated macrophages (TAM) are by now established as important regulators of tumor progression by impacting on tumor immunity, angiogenesis, and metastasis. Hence, a multitude of approaches are currently pursued to intervene with TAM's protumor activities, the most advanced of which being a blockade of macrophage-colony stimulating factor (M-CSF)/M-CSF receptor (M-CSFR) signaling. M-CSFR signaling largely impacts on the differentiation of macrophages, including TAM, and hence strongly influences the numbers of these cells in tumors. However, a repolarization of TAM toward a more antitumor phenotype may be more elegant and may yield stronger effects on tumor growth. In this respect, several aspects of TAM behavior could be altered, such as their intratumoral localization, metabolism and regulatory pathways. Intervention strategies could include the use of small molecules but also new generations of biologicals which may complement the current success of immune checkpoint blockers. This review highlights current work on the search for new therapeutic targets in TAM.

The histone demethylase KDM3A, and its downstream target MCAM, promote Ewing Sarcoma cell migration and metastasis

Ewing Sarcoma is the second most common solid pediatric malignant neoplasm of bone and soft tissue. Driven by EWS/Ets, or rarely variant, oncogenic fusions, Ewing Sarcoma is a biologically and clinically aggressive disease with a high propensity for metastasis. However, the mechanisms underpinning Ewing Sarcoma metastasis are currently not well understood. In the present study, we identify and characterize a novel metastasis-promotional pathway in Ewing Sarcoma, involving the histone demethylase KDM3A, previously identified by our laboratory as a new cancer-promoting gene in this disease. Using global gene expression profiling, we show that KDM3A positively regulates genes and pathways implicated in cell migration and metastasis, and demonstrate, using functional assays, that KDM3A promotes migration in vitro and experimental, post-intravasation, metastasis in vivo. We further identify the melanoma cell adhesion molecule (MCAM) as a novel KDM3A target gene in Ewing Sarcoma, and an important effector of KDM3A pro-metastatic action. Specifically, we demonstrate that MCAM depletion, like KDM3A depletion, inhibits cell migration in vitro and experimental metastasis in vivo, and that MCAM partially rescues impaired migration due to KDM3A knock-down. Mechanistically, we show that KDM3A regulates MCAM expression both through a direct mechanism, involving modulation of H3K9 methylation at the MCAM promoter, and an indirect mechanism, via the Ets1 transcription factor. Finally, we identify an association between high MCAM levels in patient tumors and poor survival, in two different Ewing Sarcoma clinical cohorts. Taken together, our studies uncover a new metastasis-promoting pathway in Ewing Sarcoma, with therapeutically targetable components.

Tumor-Associated Macrophages as Target for Antitumor Therapy

It is well known that the microenvironment of solid tumors is rich in inflammatory cells that influence tumor growth and development. Macrophages, called tumor-associated macrophages (TAMs), are the most abundant immune cell population present in tumor tissue. Several studies have demonstrated that the density of TAMs is associated with a poor prognosis and positively correlates with tumor growth. Several studies have proved that TAMs may activate and protect tumor stem cells, stimulate their proliferation as well as promote angiogenesis and metastasis. Furthermore, TAMs-derived cytokines and other proteins, such as CCL-17, CCL-22, TGF-β, IL-10, arginase 1, and galectin-3, make a significant contribution to immunosuppression. Since TAMs influence various aspects of cancer progression, there are many attempts to use them as a target for immunotherapy. The numerous studies have shown that the primary tumor growth and the number of metastatic sites can be significantly decreased by decreasing the population of macrophages in tumor tissue, for example, by blocking recruitment of monocytes or eliminating TAMs already present in the tumor tissue. Moreover, there are attempts at reprogramming TAMs into proinflammatory M1 macrophages or neutralizing the protumoral products of TAMs. Another approach uses TAMs for anticancer drug delivery into the tumor environment. In this review, we would like to summarize the clinical and preclinical trials that were focused on macrophages as a target for anticancer therapies.

Applying Structure-Based Drug Design Approaches to Allosteric Modulators of GPCRs

Structural insights have been revealed from X-ray co-complexes of a range of G protein-coupled receptors (GPCRs) and their allosteric ligands. The understanding of how small molecules can modulate the function of this important class of receptors by binding to a diverse range of pockets on and inside the proteins has had a profound impact on the structure-based drug design (SBDD) of new classes of therapeutic agents. The types of allosteric pockets and the mode of modulation as well as the advantages and disadvantages of targeting allosteric pockets (as opposed to the natural orthosteric site) are considered in the context of these new structural findings.

Anti-cancer effect of danshen and dihydroisotanshinone I on prostate cancer: targeting the crosstalk between macrophages and cancer cells via inhibition of the STAT3/CCL2 signaling pathway

Danshen (Salvia miltiorrhiza Bunge) is widely used in traditional Chinese medicine. In our study, the in vivo protective effect of danshen in prostate cancer patients was validated through data from the National Health Insurance Research Database in Taiwan. In vitro, we discovered that dihydroisotanshinone I (DT), a bioactive compound present in danshen, can inhibit the migration of both androgen-dependent and androgen-independent prostate cancer cells. In addition, we noted that DT substantially inhibited the migratory ability of prostate cancer cells in both a macrophage-conditioned medium and macrophage/prostate cancer coculture medium. Mechanistically, DT both diminished the ability of prostate cancer cells to recruit macrophages and reduced the secretion of chemokine (C-C motif) ligand 2 (CCL2) from both macrophages and prostate cancer cells in a dose-dependent manner. Moreover, DT inhibited the protein expression of p-STAT3 and decreased the translocation of STAT3 into nuclear chromatin. DT also suppressed the expression of tumor epithelial-mesenchymal transition genes, including RhoA and SNAI1. In conclusion, danshen can prolong the survival rate of prostate cancer patients in Taiwan. Furthermore, DT can inhibit the migration of prostate cancer cells by interrupting the crosstalk between prostate cancer cells and macrophages via the inhibition of the CCL2/STAT3 axis. These results may provide the basis for a new therapeutic approach toward the treatment of prostate cancer progression.

How Schwann cells facilitate cancer progression in nerves

Recent studies have demonstrated a critical role for nerves in enabling tumor progression. The association of nerves with cancer cells is well established for a variety of malignant tumors, including pancreatic, prostate and the head and neck cancers. This association is often correlated with poor prognosis. A strong partnership between cancer cells and nerve cells leads to both cancer progression and expansion of the nerve network. This relationship is supported by molecular pathways related to nerve growth and repair. Peripheral nerves form complex tumor microenvironments, which are made of several cell types including Schwann cells. Recent studies have revealed that Schwann cells enable cancer progression by adopting a de-differentiated phenotype, similar to the Schwann cell response to nerve trauma. A detailed understanding of the molecular and cellular mechanisms involved in the regulation of cancer progression by the nerves is essential to design strategies to inhibit tumor progression.

Insights into CC Chemokine Ligand 2/Chemokine Receptor 2 Molecular Recognition: A Step Forward toward Antichemotactic Agents

Chemokine ligand 2 (CCL2), also known as monocyte chemoattractant protein 1 (MCP-1), is a chemokine that recruits immune cells to inflammatory sites by interacting with G protein-coupled receptor CCR2. The CCL2/CCR2 axis is also involved in pathological processes such as tumor growth and metastasis and hence is currently considered as an important drug target. CCL2 exists in a dynamic monomer-dimer equilibrium that is modulated by CCR2 binding. We used solution nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations to study the interactions between CCL2 and a sulfopeptide corresponding to the N-terminal sequence of CCR2 (CCR2_18-31). Peptide binding induced the dissociation of CCL2 into monomers, forming stable CCL2/CCR2_18-31 complexes. NMR relaxation measurements indicated that residues around the CCR2_18-31 binding site, which are located at the dimer interface, undergo a complex regime of motions. NMR data were used to construct a three-dimensional structural model of the CCL2/CCR2_18-31 complex, revealing that CCR2_18-31 occupies a binding site juxtaposed to the dimer interface, partially replacing monomer-monomer contacts, explaining why CCR2_18-31 binding weakens the dimer interface and induces dissociation. We found that the main interactions governing receptor binding are highly stable salt bridges with conserved chemokine residues as well as hydrophobic interactions. These data provide new insights into the structure-function relationship of the CCL2-CCR2 interaction and may be helpful for the design of novel antichemotactic agents.

Pharmacotherapeutic Targeting of G Protein-Coupled Receptors in Oncology: Examples of Approved Therapies and Emerging Concepts

G protein-coupled receptors (GPCRs) are involved in numerous physio-pathological processes, including the stimulation of cancer progression. In this regard, it should be mentioned that although GPCRs may represent major pharmaceutical targets, only a few drugs acting as GPCR inhibitors are currently used in anti-tumor therapies. For instance, certain pro-malignancy effects mediated by GPCRs are actually counteracted by the use of small molecules and peptides that function as receptor antagonists or inverse agonists. Recently, humanized monoclonal antibodies targeting GPCRs have also been developed. Here, we review the current GPCR-targeted therapies for cancer treatment, summarizing the clinical studies that led to their official approval. We provide a broad overview of the mechanisms of action of the available anti-cancer drugs targeting gonadotropin-releasing hormone, somatostatin, chemokine, and Smoothened receptors. In addition, we discuss the anti-tumor potential of novel non-approved molecules and antibodies able to target some of the aforementioned GPCRs in different experimental models and clinical trials. Likewise, we focus on the repurposing in cancer patients of non-oncological GPCR-based drugs, elucidating the rationale behind this approach and providing clinical evidence on their safety and efficacy.

Progress in tumor-associated macrophage (TAM)-targeted therapeutics

As an essential innate immune population for maintaining body homeostasis and warding off foreign pathogens, macrophages display high plasticity and perform diverse supportive functions specialized to different tissue compartments. Consequently, aberrance in macrophage functions contributes substantially to progression of several diseases including cancer, fibrosis, and diabetes. In the context of cancer, tumor-associated macrophages (TAMs) in tumor microenvironment (TME) typically promote cancer cell proliferation, immunosuppression, and angiogenesis in support of tumor growth and metastasis. Oftentimes, the abundance of TAMs in tumor is correlated with poor disease prognosis. Hence, significant attention has been drawn towards development of cancer immunotherapies targeting these TAMs; either depleting them from tumor, blocking their pro-tumoral functions, or restoring their immunostimulatory/tumoricidal properties. This review aims to introduce readers to various aspects in development and evaluation of TAM-targeted therapeutics in pre-clinical and clinical stages.

T-independent response mediated by oncolytic tanapoxvirus recombinants expressing interleukin-2 and monocyte chemoattractant protein-1 suppresses human triple negative breast tumors

Human triple negative breast cancer (TNBC) is an aggressive disease, associated with a high rate of recurrence and metastasis. Current therapeutics for TNBC are limited, highly toxic and show inconsistent efficacy due to a high degree of intra-tumoral and inter-tumoral heterogeneity. Oncolytic viruses (OVs) are an emerging treatment option for cancers. Several OVs are currently under investigation in preclinical and clinical settings. Here, we examine the oncolytic potential of two tanapoxvirus (TPV) recombinants expressing mouse monocyte chemoattractant protein (mMCP)-1 [also known as mCCL2] and mouse interleukin (mIL)-2, in human TNBC, in vitro and in vivo. Both wild-type (wt) TPV and TPV recombinants demonstrated efficient replicability in human TNBC cells and killed cancer cell efficiently in a dose-dependent manner in vitro. TPV/∆66R/mCCL2 and TPV/∆66R/mIL-2 expressing mCCL2 and mIL-2, respectively, suppressed the growth of MDA-MB-231 tumor xenografts in nude mice significantly, as compared to the mock-injected tumors. Histological analysis of tumors showed areas of viable tumor cells, necrotic foci and immune cell accumulation in virus-treated tumors. Moreover, TPV/∆66R/mIL-2-treated tumors showed a deep infiltration of mononuclear immune cells into the tumor capsule and focal cell death in tumors. In conclusion, TPV recombinants expressing mCCL2 and mIL-2 showed a significant therapeutic effect in MDA-MB-231 tumor xenografts, in nude mice through induction of potent antitumor immune responses. Considering the oncolytic potency of armed oncolytic TPV recombinants expressing mCCL2 and mIL-2 in an experimental nude mouse model, these viruses merit further investigation as alternative treatment options for human breast cancer.

Cellular and Molecular Identity of Tumor-Associated Macrophages in Glioblastoma

In glioblastoma (GBM), tumor-associated macrophages (TAM) represent up to one half of the cells of the tumor mass, including both infiltrating macrophages and resident brain microglia. In an effort to delineate the temporal and spatial dynamics of TAM composition during gliomagenesis, we used genetically engineered and GL261-induced mouse models in combination with CX3CR1^GFP/WT;CCR2^RFP/WT double knock-in mice. Using this approach, we demonstrated that CX3CR1^LoCCR2^Hi monocytes were recruited to the GBM, where they transitioned to CX3CR1^HiCCR2^Lo macrophages and CX3CR1^HiCCR2^- microglia-like cells. Infiltrating macrophages/monocytes constituted approximately 85% of the total TAM population, with resident microglia accounting for the approximately 15% remaining. Bone marrow-derived infiltrating macrophages/monocytes were recruited to the tumor early during GBM initiation, where they localized preferentially to perivascular areas. In contrast, resident microglia were localized mainly to peritumoral regions. RNA-sequencing analyses revealed differential gene expression patterns unique to infiltrating and resident cells, suggesting unique functions for each TAM population. Notably, limiting monocyte infiltration via genetic Ccl2 reduction prolonged the survival of tumor-bearing mice. Our findings illuminate the unique composition and functions of infiltrating and resident myeloid cells in GBM, establishing a rationale to target infiltrating cells in this neoplasm. Cancer Res; 77(9); 2266-78. ©2017 AACR.

The G Protein-Coupled Receptor UT of the Neuropeptide Urotensin II Displays Structural and Functional Chemokine Features

The urotensinergic system was previously considered as being linked to numerous physiopathological states, including atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal disease, as well as brain vascular lesions. Thus, it turns out that the actions of the urotensin II (UII)/G protein-coupled receptor UT system in animal models are currently not predictive enough in regard to their effects in human clinical trials and that UII analogs, established to target UT, were not as beneficial as expected in pathological situations. Thus, many questions remain regarding the overall signaling profiles of UT leading to complex involvement in cardiovascular and inflammatory responses as well as cancer. We address the potential UT chemotactic structural and functional definition under an evolutionary angle, by the existence of a common conserved structural feature among chemokine receptorsopioïdergic receptors and UT, i.e., a specific proline position in the transmembrane domain-2 TM2 (P2.58) likely responsible for a kink helical structure that would play a key role in chemokine functions. Even if the last decade was devoted to the elucidation of the cardiovascular control by the urotensinergic system, we also attempt here to discuss the role of UII on inflammation and migration, likely providing a peptide chemokine status for UII. Indeed, our recent work established that activation of UT by a gradient concentration of UII recruits Gαi/o and Gα13 couplings in a spatiotemporal way, controlling key signaling events leading to chemotaxis. We think that this new vision of the urotensinergic system should help considering UT as a chemotactic therapeutic target in pathological situations involving cell chemoattraction.

Structure of CC chemokine receptor 2 with orthosteric and allosteric antagonists

CC chemokine receptor 2 (CCR2) is one of 19 members of the chemokine receptor subfamily of human class A G-protein-coupled receptors. CCR2 is expressed on monocytes, immature dendritic cells, and T-cell subpopulations, and mediates their migration towards endogenous CC chemokine ligands such as CCL2 (ref. 1). CCR2 and its ligands are implicated in numerous inflammatory and neurodegenerative diseases including atherosclerosis, multiple sclerosis, asthma, neuropathic pain, and diabetic nephropathy, as well as cancer. These disease associations have motivated numerous preclinical studies and clinical trials (see http://www.clinicaltrials.gov) in search of therapies that target the CCR2-chemokine axis. To aid drug discovery efforts, here we solve a structure of CCR2 in a ternary complex with an orthosteric (BMS-681 (ref. 6)) and allosteric (CCR2-RA-[R]) antagonist. BMS-681 inhibits chemokine binding by occupying the orthosteric pocket of the receptor in a previously unseen binding mode. CCR2-RA-[R] binds in a novel, highly druggable pocket that is the most intracellular allosteric site observed in class A G-protein-coupled receptors so far; this site spatially overlaps the G-protein-binding site in homologous receptors. CCR2-RA-[R] inhibits CCR2 non-competitively by blocking activation-associated conformational changes and formation of the G-protein-binding interface. The conformational signature of the conserved microswitch residues observed in double-antagonist-bound CCR2 resembles the most inactive G-protein-coupled receptor structures solved so far. Like other protein-protein interactions, receptor-chemokine complexes are considered challenging therapeutic targets for small molecules, and the present structure suggests diverse pocket epitopes that can be exploited to overcome obstacles in drug design.

Molecular Pathways: Deciphering Mechanisms of Resistance to Macrophage-Targeted Therapies

Tumor-associated macrophages (TAMs) are a major cellular component of numerous tumor types. TAM-targeted therapies include depletion strategies, inhibiting their effector functions or reprogramming toward an antitumorigenic phenotype, with varying degrees of efficacy. Here, we review preclinical and clinical strategies to target macrophages in cancer and discuss potential explanations for why some strategies are effective while other approaches have shown limited success. Clin Cancer Res; 23(4); 876-84. ©2016 AACR.

Targeting inflammasome/IL-1 pathways for cancer immunotherapy

The inflammatory microenvironment has been shown to play important roles in various stages of tumor development including initiation, growth, and metastasis. The inflammasome is a critical innate immune pathway for the production of active IL-1β, a potent inflammatory cytokine. Although inflammasomes are essential for host defense against pathogens and contribute to autoimmune diseases, their role in tumor progression remains controversial. Here, our results demonstrate that the inflammasome and IL-1β pathway promoted tumor growth and metastasis in animal and human breast cancer models. We found that tumor progression was associated with the activation of inflammasome and elevated levels of IL-1β at primary and metastatic sites. Mice deficient for inflammasome components exhibited significantly reduced tumor growth and lung metastasis. Furthermore, inflammasome activation promoted the infiltration of myeloid cells such as myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) into tumor microenvironments. Importantly, blocking IL-1R with IL-1R antagonist (IL-Ra) inhibited tumor growth and metastasis accompanied by decreased myeloid cell accumulation. Our results suggest that targeting the inflammasome/IL-1 pathway in tumor microenvironments may provide a novel approach for the treatment of cancer.

Chemokines, cytokines and exosomes help tumors to shape inflammatory microenvironment

Relationship between inflammation and cancer is now well-established and represents a paradigm that our immune response does not necessarily serves solely to protect us from infections and cancer. Many specific mechanisms that link chronic inflammation to cancer promotion and metastasis have been uncovered in the recent years. Here we are focusing on the effects that tumors may exert on inflammatory cascades, tuning the immune system ability to cause tumor promotion or regression. In particular, we discuss the contributions of chemokines, cytokines and exosomes to the processes such as induction of inflammation and tumorigenesis. Overall, tumor-elicited inflammation is a key driver of tumor progression and an essential component of tumor microenvironment.

Identification of key pathways and genes in colorectal cancer using bioinformatics analysis

Colorectal cancer (CRC) is the most common malignant tumor of digestive system. The aim of this study was to identify gene signatures during CRC and uncover their potential mechanisms. The gene expression profiles of GSE21815 were downloaded from GEO database. The GSE21815 dataset contained 141 samples, including 132 CRC and 9 normal colon epitheliums. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed, and protein-protein interaction (PPI) network of the differentially expressed genes (DEGs) was constructed by Cytoscape software. In total, 3500 DEGs were identified in CRC, including 1370 up-regulated genes and 2130 down-regulated genes. GO analysis results showed that up-regulated DEGs were significantly enriched in biological processes (BP), including cell cycle, cell division, and cell proliferation; the down-regulated DEGs were significantly enriched in biological processes, including immune response, intracellular signaling cascade and defense response. KEGG pathway analysis showed the up-regulated DEGs were enriched in cell cycle and DNA replication, while the down-regulated DEGs were enriched in drug metabolism, metabolism of xenobiotics by cytochrome P450, and retinol metabolism pathways. The top 10 hub genes, GNG2, AGT, SAA1, ADCY5, LPAR1, NMU, IL8, CXCL12, GNAI1, and CCR2 were identified from the PPI network, and sub-networks revealed these genes were involved in significant pathways, including G protein-coupled receptors signaling pathway, gastrin-CREB signaling pathway via PKC and MAPK, and extracellular matrix organization. In conclusion, the present study indicated that the identified DEGs and hub genes promote our understanding of the molecular mechanisms underlying the development of CRC, and might be used as molecular targets and diagnostic biomarkers for the treatment of CRC.