Targeting of tumour-infiltrating macrophages via CCL2/CCR2 signalling as a therapeutic strategy against hepatocellular carcinoma

Disruption of FBXL5-mediated cellular iron homeostasis promotes liver carcinogenesis

Hepatocellular iron overload elicited by ablation of the iron-sensing ubiquitin ligase FBXL5 promotes liver carcinogenesis induced by exposure to a chemical carcinogen or hepatitis virus, suggesting that FBXL5 is a previously unrecognized oncosuppressor in liver carcinogenesis in mice.

Hepatic iron overload is a risk factor for progression of hepatocellular carcinoma (HCC), although the molecular mechanisms underlying this association have remained unclear. We now show that the iron-sensing ubiquitin ligase FBXL5 is a previously unrecognized oncosuppressor in liver carcinogenesis in mice. Hepatocellular iron overload elicited by FBXL5 ablation gave rise to oxidative stress, tissue damage, inflammation, and compensatory proliferation of hepatocytes and to consequent promotion of liver carcinogenesis induced by exposure to a chemical carcinogen. The tumor-promoting outcome of FBXL5 deficiency in the liver was also found to be effective in a model of virus-induced HCC. FBXL5-deficient mice thus constitute the first genetically engineered mouse model of liver carcinogenesis promoted by iron overload. In addition, dysregulation of FBXL5-mediated cellular iron homeostasis was found to be associated with poor prognosis in human HCC, suggesting that FBXL5 plays a key role in defense against hepatocarcinogenesis.

Chemokines and Chemokine Receptors: New Targets for Cancer Immunotherapy

Immunotherapy is a clinically validated treatment for many cancers to boost the immune system against tumor growth and dissemination. Several strategies are used to harness immune cells: monoclonal antibodies against tumor antigens, immune checkpoint inhibitors, vaccination, adoptive cell therapies (e.g., CAR-T cells) and cytokine administration. In the last decades, it is emerging that the chemokine system represents a potential target for immunotherapy. Chemokines, a large family of cytokines with chemotactic activity, and their cognate receptors are expressed by both cancer and stromal cells. Their altered expression in malignancies dictates leukocyte recruitment and activation, angiogenesis, cancer cell proliferation, and metastasis in all the stages of the disease. Here, we review first attempts to inhibit the chemokine system in cancer as a monotherapy or in combination with canonical or immuno-mediated therapies. We also provide recent findings about the role in cancer of atypical chemokine receptors that could become future targets for immunotherapy.

The role of macrophages in nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) and its inflammatory and often progressive subtype nonalcoholic steatohepatitis (NASH) are becoming the leading cause of liver-related morbidity and mortality worldwide, and a primary indication for liver transplantation. The pathophysiology of NASH is multifactorial and not yet completely understood; however, innate immunity is a major contributing factor in which liver-resident macrophages (Kupffer cells) and recruited macrophages play a central part in disease progression. In this Review, we assess the evidence for macrophage involvement in the development of steatosis, inflammation and fibrosis in NASH. In this process, not only the polarization of liver macrophages towards a pro-inflammatory phenotype is important, but adipose tissue macrophages, especially in the visceral compartment, also contribute to disease severity and insulin resistance. Macrophage activation is mediated by factors such as endotoxins and translocated bacteria owing to increased intestinal permeability, factors released from damaged or lipoapoptotic hepatocytes, as well as alterations in gut microbiota and defined nutritional components, including certain free fatty acids, cholesterol and their metabolites. Reflecting the important role of macrophages in NASH, we also review studies investigating drugs that target macrophage recruitment to the liver, macrophage polarization and their inflammatory effects as potential treatment options for patients with NASH.

LncRNA-MM2P Identified as a Modulator of Macrophage M2 Polarization

M2 polarization of macrophages is essential for their function in immunologic tolerance, which might promote tumorigenesis. However, the molecular mechanism behind the polarization process is not fully understood. Given that several lines of evidence have suggested that long noncoding RNAs (lncRNAs) could be involved in regulating immune cell differentiation and function, the current study aimed to identify the lncRNAs that specifically modulate M2 macrophage polarization. By utilizing a series of cell-based M2 macrophage polarization models, a total of 25 lncRNAs with altered expression were documented based on lncRNA microarray-based profiling assays. Among them, lncRNA-MM2P was the only lncRNA upregulated during M2 polarization but downregulated in M1 macrophages. Knockdown of lncRNA-MM2P blocked cytokine-driven M2 polarization of macrophages and weakened the angiogenesis-promoting feature of M2 macrophages by reducing phosphorylation on STAT6. Moreover, manipulating lncRNA-MM2P in macrophages impaired macrophage-mediated promotion of tumorigenesis, tumor growth in vivo, and tumor angiogenesis. Collectively, our study identifies lncRNA-MM2P as a modulator required for macrophage M2 polarization and uncovers its role in macrophage-promoted tumorigenesis.

CCL15 Recruits Suppressive Monocytes to Facilitate Immune Escape and Disease Progression in Hepatocellular Carcinoma

Chemokines play a key role in orchestrating the recruitment and positioning of myeloid cells within the tumor microenvironment. However, the tropism regulation and functions of these cells in hepatocellular carcinoma (HCC) are not completely understood. Herein, by scrutinizing the expression of all chemokines in HCC cell lines and tissues, we found that CCL15 was the most abundantly expressed chemokine in human HCC. Further analyses showed that CCL15 expression was regulated by genetic, epigenetic, and microenvironmental factors, and negatively correlated with patient clinical outcome. In addition to promoting tumor invasion in an autocrine manner, CCL15 specifically recruited CCR1+ cells toward HCC invasive margin, approximately 80% of which were CD14+ monocytes. Clinically, a high density of marginal CCR1+ CD14+ monocytes positively correlated with CCL15 expression and was an independent index for dismal survival. Functionally, these tumor-educated monocytes directly accelerated tumor invasion and metastasis through bursting various pro-tumor factors and activating signal transducer and activator of transcription 1/3, extracellular signal-regulated kinase 1/2, and v-akt murine thymoma viral oncogene homolog signaling in HCC cells. Meanwhile, tumor-derived CCR1+ CD14+ monocytes expressed significantly higher levels of programmed cell death-ligand 1, B7-H3, and T-cell immunoglobulin domain and mucin domain-3 that may lead to immune suppression. Transcriptome sequencing confirmed that tumor-infiltrating CCR1+ CD14+ monocytes were reprogrammed to upregulate immune checkpoints, immune tolerogenic metabolic enzymes (indoleamine and arginase), inflammatory/pro-angiogenic cytokines, matrix remodeling proteases, and inflammatory chemokines. Orthotopic animal models confirmed that CCL15-CCR1 axis forested an inflammatory microenvironment enriched with CCR1+ monocytes and led to increased metastatic potential of HCC cells. Conclusion: A complex tumor-promoting inflammatory microenvironment was shaped by CCL15-CCR1 axis in human HCC. Blockade of CCL15-CCR1 axis in HCC could be an effective anticancer therapy.

STAT3 inhibition reduces macrophage number and tumor growth in neurofibroma

Plexiform neurofibroma, a benign peripheral nerve tumor, is associated with the biallelic loss of function of the NF1 tumor suppressor in Schwann cells. Here, we show that FLLL32, a small molecule inhibitor of JAK/STAT3 signaling, reduces neurofibroma growth in mice with conditional, biallelic deletion of Nf1 in the Schwann cell lineage. FLLL32 treatment or Stat3 deletion in tumor cells reduced inflammatory cytokine expression and tumor macrophage numbers in neurofibroma. Although STAT3 inhibition down-regulated the chemokines CCL2 and CCL12, which can signal through CCR2 to recruit macrophages to peripheral nerves, deletion of Ccr2 did not improve survival or reduce macrophage numbers in neurofibroma-bearing mice. Interestingly, macrophages accounted for ~20-40% of proliferating cells in untreated tumors. FLLL32 suppressed this proliferation, as well as Schwann cell proliferation, implicating STAT3-dependent, local proliferation in neurofibroma macrophage accumulation. The functions of STAT3 signaling in neurofibroma Schwann cells and macrophages, and its relevance as a therapeutic target in neurofibroma, merit further investigation.

Prognostic significance of monocyte chemoattractant protein-1 and CC chemokine receptor 2 in diffuse large B cell lymphoma

Aberrant monocyte chemoattractant protein-1 (MCP-1) and CC chemokine receptor 2 (CCR2) expression in malignant tissues have been reported; however, their role in hematological malignancies prognosis remains little known. The aim of this study was to investigate the prognostic value of MCP-1 and CCR2 expression in patients with diffuse large B cell lymphoma (DLBCL). The study included 221 patients with DLBCL. MCP-1 and CCR2 expression was analyzed by immunohistochemical staining and its correlations with clinicopathologic features and prognosis were evaluated. High expression of MCP-1 or CCR2 was correlated with clinicopathological characteristics, and an adverse prognostic factor for overall survival (OS) and progression-free survival (PFS) of DLBCL patients. Also, significant positive correlation between MCP-1 and CCR2 expression was revealed (r = 0.545, P < 0.001). Patients with high MCP-1 or high CCR2 expression had significantly poorer OS and PFS than those with low MCP-1 or low CCR2 expression (OS: P < 0.001, P < 0.001; PFS: P < 0.001, P < 0.001), respectively, even in the rituximab era, and MCP-1 or CCR2 expression could further identify high-risk patients otherwise classified as low/intermediate risk by the International Prognostic Index (IPI) alone. Furthermore, incorporation of MCP-1 or CCR2 expression into the IPI score could improve prognostic value for OS. This is the first report describing the clinicopathological features and survival outcome according to expression of MCP-1 and CCR2 in DLBCL.

An isoform of AIF1 involved in breast cancer

Background

Inflammation is a major player in breast cancer (BC) progression. Allograft-inflammatory factor-1 (AIF1) is a crucial mediator in the inflammatory response. AIF1 reportedly plays a role in BC, but the mechanism remains to be elucidated. We identified two AIF1 isoforms, AIF1v1 and AIF1v3, which were differentially expressed between affected and unaffected sisters from families with high risk of BC with no deleterious BRCA1/BRCA2 mutations (BRCAX). We investigated potential functions of AIFv1/v3 in BC of varying severity and breast adipose tissue by evaluating their expression, and association with metabolic and clinical parameters of BC patients.

Methods

AIF1v1/v3 expression was determined in BC tissues and cell lines using quantitative real-time PCR. Potential roles and mechanisms were examined in the microenvironment (fibroblasts, adipose tissue, monocytes and macrophages), inflammatory response (cell reaction in BC subgroups), and metabolism [treatment with docosahexaenoic acid (DHA)]. Association of AIF1 transcript expression with clinical factors was determined by Spearman’s rank correlation. Bioinformatics analyses were performed to characterize transcripts.

Results

AIF1v1/v3 were mostly expressed in the less severe BC samples, and their expression appeared to originate from the tumor microenvironment. AIF1 isoforms had different expression rates and sources in breast adipose tissue; lymphocytes mostly expressed AIF1v1 while activated macrophages mainly expressed AIF1v3. Bioinformatics analysis revealed major structural differences suggesting distinct functions in BC progression. Lymphocytes were the most infiltrating cells in breast tumors and their number correlated with AIF1v1 adipose expression. Furthermore, DHA supplementation significantly lowered the expression of AIF1 isoforms in BRCAX cell lines. Finally, the expression of AIF1 isoforms in BC and breast adipose tissue correlated with clinical parameters of BC patients.

Conclusions

Results strongly suggest that AIF1v1 as much as AIF1v3 play a major role in the crosstalk between BC and infiltrating immune cells mediating tumor progression, implying their high potential as target molecules for BC diagnostic, prognostication and treatment.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0663-3) contains supplementary material, which is available to authorized users.

Tumor-associated macrophages promote lung metastasis and induce epithelial-mesenchymal transition in osteosarcoma by activating the COX-2/STAT3 axis

Osteosarcoma (OS) is a common, malignant musculoskeletal tumor in young people. Neoadjuvant chemotherapy has improved the survival of osteosarcoma patients but with limited benefit due to metastasis. Tumor-associated macrophages (TAMs) are involved in various mechanisms of tumor biology, which include oncogenesis, drug resistance, and tumor immune escape, as well as tumor metastasis. In this study, we proved that TAMs possess the ability to promote OS cell migration and invasion by upregulating COX-2, MMP9, and phosphorylated STAT3 and to induce the epithelial-mesenchymal transition (EMT). This evidence has also been verified in a tumor-bearing animal model, and in OS patients. Furthermore, we observed the anti-metastasis effect of COX-2 inhibition by repressing COX-2 expression, EMT-activating transcription factors and the STAT3 pathway, both in vitro and in vivo. We propose that TAMs promote OS metastasis and invasion by activating the COX-2/STAT3 axis and EMT. These findings suggest that TAMs and COX-2 may be potential targets for future anti-metastasis therapy.

The CCR2+ Macrophage Subset Promotes Pathogenic Angiogenesis for Tumor Vascularization in Fibrotic Livers

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) typically arises in fibrotic or cirrhotic livers, which are characterized by pathogenic angiogenesis. Myeloid immune cells, specifically tumor-associated macrophages (TAMs), may represent potential novel therapeutic targets in HCC, complementing current ablative or immune therapies. However, the detailed functions of TAM subsets in hepatocarcinogenesis have remained obscure.

METHODS

TAM subsets were analyzed in-depth in human HCC samples and a combined fibrosis-HCC mouse model, established by i.p. injection with diethylnitrosamine after birth and repetitive carbon tetrachloride (CCl₄) treatment for 16 weeks. Based on comprehensively phenotyping TAM subsets (fluorescence-activated cell sorter, transcriptomics) in mice, the function of CCR2⁺ TAM was assessed by a pharmacologic chemokine inhibitor. Angiogenesis was evaluated by contrast-enhanced micro-computed tomography and histology.

RESULTS

We show that human CCR2⁺ TAM accumulate at the highly vascularized HCC border and express the inflammatory marker S100A9, whereas CD163⁺ immune-suppressive TAM accrue in the HCC center. In the fibrosis-cancer mouse model, we identified 3 major hepatic myeloid cell populations with distinct messenger RNA profiles, of which CCR2⁺ TAM particularly showed activated inflammatory and angiogenic pathways. Inhibiting CCR2⁺ TAM infiltration using a pharmacologic chemokine CCL2 antagonist in the fibrosis-HCC model significantly reduced pathogenic vascularization and hepatic blood volume, alongside attenuated tumor volume.

CONCLUSIONS

The HCC microenvironment in human patients and mice is characterized by functionally distinct macrophage populations, of which the CCR2⁺ inflammatory TAM subset has pro-angiogenic properties. Understanding the functional differentiation of myeloid cell subsets in chronically inflamed liver may provide novel opportunities for modulating hepatic macrophages to inhibit tumor-promoting pathogenic angiogenesis.

Preclinical and Clinical Therapeutic Strategies Affecting Tumor-Associated Macrophages in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) most often develops in patients with underlying liver disease characterized by chronic nonresolving inflammation. Tumor-associated macrophages (TAMs) are one of the most abundant immune cell populations within the tumoral microenvironment. As key actors of cancer-related inflammation, they promote tumor growth by suppression of effective anticancer immunity, stimulation of angiogenesis, and tissue remodeling. Therefore, they have become an attractive and promising target for immunotherapy. The heterogeneity of TAM subtypes and their origin and dynamic phenotype during the initiation and progression of HCC has been partially unraveled and forms the base for the development of therapeutic agents. Current approaches are aimed at decreasing the population of TAMs by depleting macrophages present in the tumor, blocking the recruitment of bone marrow-derived monocytes, and/or functionally reprogramming TAMs to antitumoral behavior. In this review, the preclinical evolution and hitherto clinical trials for TAM-targeted therapy in HCC will be highlighted.

LNMAT1 promotes lymphatic metastasis of bladder cancer via CCL2 dependent macrophage recruitment

Tumor-associated macrophages (TAMs) are the most abundant inflammatory infiltrates in the tumor microenvironment and contribute to lymph node (LN) metastasis. However, the precise mechanisms of TAMs-induced LN metastasis remain largely unknown. Herein, we identify a long noncoding RNA, termed Lymph Node Metastasis Associated Transcript 1 (LNMAT1), which is upregulated in LN-positive bladder cancer and associated with LN metastasis and prognosis. Through gain and loss of function approaches, we find that LNMAT1 promotes bladder cancer-associated lymphangiogenesis and lymphatic metastasis. Mechanistically, LNMAT1 epigenetically activates CCL2 expression by recruiting hnRNPL to CCL2 promoter, which leads to increased H3K4 tri-methylation that ensures hnRNPL binding and enhances transcription. Furthermore, LNMAT1-induced upregulation of CCL2 recruits macrophages into the tumor, which promotes lymphatic metastasis via VEGF-C excretion. These findings provide a plausible mechanism for LNMAT1-modulated tumor microenvironment in lymphatic metastasis and suggest that LNMAT1 may represent a potential therapeutic target for clinical intervention in LN-metastatic bladder cancer.

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.

Hepatic Hippo signaling inhibits protumoural microenvironment to suppress hepatocellular carcinoma

OBJECTIVE

Hippo signalling is a recently identified major oncosuppressive pathway that plays critical roles in inhibiting hepatocyte proliferation, survival and hepatocellular carcinoma (HCC) formation. Hippo kinase (Mst1 and Mst2) inhibits HCC proliferation by suppressing Yap/Taz transcription activities. As human HCC is mainly driven by chronic liver inflammation, it is not clear whether Hippo signalling inhibits HCC by shaping its inflammatory microenvironment.

DESIGN

We have established a genetic HCC model by deleting Mst1 and Mst2 in hepatocytes. Functions of inflammatory responses in this model were characterised by molecular, cellular and FACS analysis, immunohistochemistry and genetic deletion of monocyte chemoattractant protein-1 (Mcp1) or Yap. Human HCC databases and human HCC samples were analysed by immunohistochemistry.

RESULTS

Genetic deletion of Mst1 and Mst2 in hepatocytes (DKO) led to HCC development, highly upregulated Mcp1 expression and massive infiltration of macrophages with mixed M1 and M2 phenotypes. Macrophage ablation or deletion of Mcp1 in DKO mice markedly reduced hepatic inflammation and HCC development. Moreover, Yap removal abolished induction of Mcp1 expression and restored normal liver growth in the Mst1/Mst2 DKO mice. Finally, we showed that MCP1 is a direct transcription target of YAP in hepatocytes and identified a strong gene expression correlation between YAP targets and MCP-1 in human HCCs.

CONCLUSIONS

Hippo signalling in hepatocytes maintains normal liver growth by suppressing macrophage infiltration during protumoural microenvironment formation through the inhibition of Yap-dependent Mcp1 expression, providing new targets and strategies to treat HCCs.

Immune Gene Expression Profile in Hepatocellular Carcinoma and Surrounding Tissue Predicts Time to Tumor Recurrence

BACKGROUND

The antitumor immune response may play a major role in the clinical outcome of hepatocellular carcinoma (HCC). We characterized the liver immune microenvironment by direct hybridization of RNA extracted from HCC and nontumorous tissues.

METHODS

RNA was extracted from frozen liver tissue samples of HCC (T; n = 30) and nontumorous tissues (NT; n = 33) obtained from 38 patients. Matched samples were available for 25 patients. The immune gene expression profile was analyzed with the nCounter GX Human Immunology v2 system (NanoString Technologies), which detects the expression levels of 579 immune response-related genes simultaneously.

RESULTS

Since the immune gene expression profile of T and NT tissues was significantly different, the prognostic relevance of the liver immune microenvironment was evaluated in the T and NT samples separately. Unsupervised clustering detected two main clusters of immune gene expression both in T and in NT liver samples. In both cases, the expression clusters identified groups of patients with a significantly different median time to HCC recurrence (TTR) but similar overall survival. Based on T tissue, two groups with median TTR of 19 and 127 months, respectively, were detected (p < 0.005). Expression of genes related to T-cell activation was associated with longer TTR. The analysis of NT tissue discriminated subsets of patients with median TTR of 22 and 68 months (p < 0.05). In contrast to T tissue, a predominant inflammatory immune environment was associated with shorter TTR.

CONCLUSIONS

Immune gene expression profiles predictive of TTR could be identified both in HCC and in adjacent cirrhotic tissues. Longer TTR was associated with overexpression in T tissue and downregulation in NT tissue of the immune response and of inflammation-related genes.

Molecular profiles of tumor contrast enhancement: A radiogenomic analysis in anaplastic gliomas

The presence of contrast enhancement (CE) on magnetic resonance (MR) imaging is conventionally regarded as an indicator for tumor malignancy. However, the biological behaviors and molecular mechanism of enhanced tumor are not well illustrated. The aim of this study was to investigate the molecular profiles associated with anaplastic gliomas (AGs) presenting CE on postcontrast T1‐weighted MR imaging. In this retrospective database study, RNA sequencing and MR imaging data of 91 AGs from the Cancer Genome Atlas (TCGA) and 64 from the Chinese Glioma Genome Atlas (CGGA) were collected. Gene set enrichment analysis (GSEA), significant analysis of microarray, generalized linear models, and Least absolute shrinkage and selection operator algorithm were used to explore radiogenomic and prognostic signatures of AG patients. GSEA indicated that angiogenesis and epithelial‐mesenchymal transition were significantly associated with post‐CE. Genes driving immune system response, cell proliferation, and focal adhesions were also significantly enriched. Gene ontology of 237 differential genes indicated consistent results. A 48‐gene signature for CE was identified in TCGA and validated in CGGA dataset (area under the curve = 0.9787). Furthermore, seven genes derived from the CE‐specific signature could stratify AG patients into two subgroups based on overall survival time according to corresponding risk score. Comprehensive analysis of post‐CE and genomic characteristics leads to a better understanding of radiology‐pathology correlations. Our gene signature helps interpret the occurrence of radiological traits and predict clinical outcomes. Additionally, we found nine prognostic quantitative radiomic features of CE and investigated the underlying biological processes of them.

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.

Noncanonical Pathway for Regulation of CCL2 Expression by an mTORC1-FOXK1 Axis Promotes Recruitment of Tumor-Associated Macrophages

C-C chemokine ligand 2 (CCL2) plays pivotal roles in tumor formation, progression, and metastasis. Although CCL2 expression has been found to be dependent on the nuclear factor (NF)-κB signaling pathway, the regulation of CCL2 production in tumor cells has remained unclear. We have identified a noncanonical pathway for regulation of CCL2 production that is mediated by mammalian target of rapamycin complex 1 (mTORC1) but independent of NF-κB. Multiple phosphoproteomics approaches identified the transcription factor forkhead box K1 (FOXK1) as a downstream target of mTORC1. Activation of mTORC1 induces dephosphorylation of FOXK1, resulting in transactivation of the CCL2 gene. Inhibition of the mTORC1-FOXK1 axis attenuated insulin-induced CCL2 production as well as the accumulation of tumor-associated monocytes-macrophages and tumor progression in mice. Our results suggest that FOXK1 directly links mTORC1 signaling and CCL2 expression in a manner independent of NF-κB and that CCL2 produced by this pathway contributes to tumor progression.

The contribution of tumor-associated macrophages in glioma neo-angiogenesis and implications for anti-angiogenic strategies

"Tumor-associated macrophages" (TAMs) form a significant cell population in malignant tumors and contribute to tumor growth, metastasis, and neovascularization. Gliomas are characterized by extensive neo-angiogenesis, and knowledge of the role of TAMs in neovascularization is important for future anti-angiogenic therapies. The phenotypes and functions of TAMs are heterogeneous and more complex than a classification into M1 and M2 inflammation response types would suggest. In this review, we provide an update on the current knowledge of the ontogeny of TAMs, focusing on diffuse gliomas. The role of TAMs in the regulation of the different processes in tumor angiogenesis is highlighted and the most recently discovered mechanisms by which TAMs mediate resistance against current antivascular therapies are mentioned. Novel compounds tested in clinical trials are discussed and brought in relation to different TAM-related angiogenesis pathways. In addition, potential therapeutic targets used to intervene in TAM-regulated tumor angiogenesis are summarized.

Synergy between peroxisome proliferator-activated receptor γ agonist and radiotherapy in cancer

Angiogenesis and inflammation are crucial processes through which the tumor microenvironment (TME) influences tumor progression. In this study, we showed that peroxisome proliferator‐activated receptor γ (PPARγ) is not only expressed in CT26 and 4T1 tumor cell lines but also in cells of TME, including endothelial cells and tumor‐associated macrophages (TAM). In addition, we showed that rosiglitazone may induce tumor vessel normalization and reduce TAM infiltration. Additionally, 4T1 and CT26 tumor‐bearing mice treated with rosiglitazone in combination with radiotherapy showed a significant reduction in lesion size and lung metastasis. We reported that a single dose of 12 Gy irradiation strongly inhibits local tumor angiogenesis. Secretion of C‐C motif chemokine ligand 2 (CCL2) in response to local irradiation facilitates the recruitment of migrating CD11b⁺ myeloid monocytes and TAM to irradiated sites that initiate vasculogenesis and enable tumor recurrence after radiotherapy. We found that rosiglitazone partially decreases CCL2 secretion by tumor cells and reduces the infiltration of CD11b⁺ myeloid monocytes and TAM to irradiated tumors, thereby delaying tumor regrowth after radiotherapy. Therefore, combination of the PPARγ agonist rosiglitazone with radiotherapy enhances the effectiveness of radiotherapy to improve local tumor control, decrease distant metastasis risks and delay tumor recurrence.

Chronic liver injury promotes hepatocarcinoma cell seeding and growth, associated with infiltration by macrophages

Ninety percent of hepatocarcinoma (HCC) develops in a chronically damaged liver. Interactions between non‐tumor stromal components, especially macrophages, and cancer cells are still incompletely understood. Our aim was to determine whether a chronically injured liver represents a favorable environment for the seeding and growth of HCC cells, and to evaluate the potential roles of macrophages infiltrated within the tumor. HCC cells were injected into the liver in healthy mice (healthy liver group [HL]) and in mice chronically treated with carbon tetrachloride (CCl₄) for 7 weeks (CCl₄ 7w group). Livers were examined for the presence of tumor 2 weeks post‐injection. Tumor and non‐tumor tissues were analyzed for macrophage infiltration, origin (monocytes‐derived vs resident macrophages) and polarization state, and MMP production. Fifty‐three percent of mice developed neoplastic lesion in the HL group whereas a tumor lesion was found in all livers in the CCl₄ 7w group. Macrophages infiltrated more deeply the tumors of the CCl₄ 7w group. Evaluation of factors involved in the recruitment of macrophages and of markers of their polarization state was in favor of prominent infiltration of M2 pro‐tumor monocyte‐derived macrophages inside the tumors developing in a chronically injured liver. MMP‐2 and ‐9 production, attributed to M2 pro‐tumor macrophages, was significantly higher in the tumors of the CCl₄ 7w group. In our model, chronic liver damage promotes cancer development. Our results suggest that an injured background favors the infiltration of M2 pro‐tumor monocyte‐derived macrophages. These secrete MMP‐2 and MMP‐9 that promote tumor progression.

Targeting CCR2 with its antagonist suppresses viability, motility and invasion by downregulating MMP-9 expression in non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, which is the leading cancer killer in the world. Despite the recent advances in its diagnosis and therapy, the prognosis of NSCLC patients remains very poor, mainly due to the development of drug resistance and metastasis. Both the chemokine network and the matrix metalloproteinase (MMP) system play important roles in cancer cell metastasis. The disruption of CCL2/CCR2 chemokine signaling has been shown to suppress cancer cellviability and metastasis. CCL2-neutralizing antibodies, which have shown promising therapeutic efficacy in several cancer models, are not widely used due to technical issues. CCR2 antagonism has thus become an alternative method for cancer treatment. However, the effect of CCR2 antagonists on NSCLC progression remains poorly understood. Here, we investigated the effect of CCR2 antagonist (CAS445479-97-0) on the proliferation, migration and invasion of human lung adenocarcinoma A549 cells by using WST-1 cell viability assay, transwell migration assay, wound healing scratch assay and Matrigel invasion assay. We demonstrated that CCL2 treatment promoted A549 cell viability, motility and invasion by upregulating MMP-9 expression and that this induction was significantly suppressed by CAS 445479-97-0. Taken together, our data suggested that the CCR2 antagonist would be a potential drug for treating CCR2-positive NSCLC patients.

CCL2-SQSTM1 positive feedback loop suppresses autophagy to promote chemoresistance in gastric cancer

Chemotherapy is one of the most important approaches for the treatment of various cancers. However, tumor cells often develop resistance to chemotherapeutic drugs. The tumor microenvironment reconstituted by various cytokines secreted from immune cells was recently found to play important roles in affecting therapeutic response of tumor cells. Herein, we reported that tumor cells can secrete autocrine cytokines to confer chemoresistance by inactivating proapoptotic autophagy. Through cytokine screening, we found that drug resistant cancer cells secreted more CCL2 than drug sensitive cells. Such secreted CCL2 could not only maintain chemoresistance in drug-resistant cancer cells but also confer drug resistance to drug-sensitive cancer cells. CCL2 attenuated drug-induced cytotoxicity by activating PI3K-Akt-mTOR signaling to inhibit proapoptotic autophagy and increase SQSTM1 expression. CCL2 expression in primary carcinoma tissues also correlated well with SQSTM1 expression. Either CCL2 knock-down or autophagy induction successfully reversed drug resistance of tumor cells. Moreover, increased expression of SQSTM1 in turn activated CCL2 transcription via NF-κB signal pathway, representing a positive feedback loop to maintain drug resistance. Therefore, our results provided a new insight to understand drug resistance, and indicated the potential value of CCL2 as a biomarker and intervention target for chemotherapy resistance.

Emerging Roles of G Protein-Coupled Receptors in Hepatocellular Carcinoma

Among a great variety of cell surface receptors, the largest superfamily is G protein-coupled receptors (GPCRs), also known as seven-transmembrane domain receptors. GPCRs can modulate diverse signal-transduction pathways through G protein-dependent or independent pathways which involve &beta;-arrestins, G protein receptor kinases (GRKs), ion channels, or Src kinases under physiological and pathological conditions. Recent studies have revealed the crucial role of GPCRs in the tumorigenesis and the development of cancer metastasis. We will sum up the functions of GPCRs&mdash;particularly those coupled to chemokines, prostaglandin, lysophosphatidic acid, endothelin, catecholamine, and angiotensin&mdash;in the proliferation, invasion, metastasis, and angiogenesis of hepatoma cells and the development of hepatocellular carcinoma (HCC) in this review. We also highlight the potential avenues of GPCR-based therapeutics for HCC.

Contribution to Tumor Angiogenesis From Innate Immune Cells Within the Tumor Microenvironment: Implications for Immunotherapy

The critical role of angiogenesis in promoting tumor growth and metastasis is strongly established. However, tumors show considerable variation in angiogenic characteristics and in their sensitivity to antiangiogenic therapy. Tumor angiogenesis involves not only cancer cells but also various tumor-associated leukocytes (TALs) and stromal cells. TALs produce chemokines, cytokines, proteases, structural proteins, and microvescicles. Vascular endothelial growth factor (VEGF) and inflammatory chemokines are not only major proangiogenic factors but are also immune modulators, which increase angiogenesis and lead to immune suppression. In our review, we discuss the regulation of angiogenesis by innate immune cells in the tumor microenvironment, specific features, and roles of major players: macrophages, neutrophils, myeloid-derived suppressor and dendritic cells, mast cells, γδT cells, innate lymphoid cells, and natural killer cells. Anti-VEGF or anti-inflammatory drugs could balance an immunosuppressive microenvironment to an immune permissive one. Anti-VEGF as well as anti-inflammatory drugs could therefore represent partners for combinations with immune checkpoint inhibitors, enhancing the effects of immune therapy.

Macrophage Polarization in Chronic Inflammatory Diseases: Killers or Builders?

Macrophages are key cellular components of the innate immunity, acting as the main player in the first-line defence against the pathogens and modulating homeostatic and inflammatory responses. Plasticity is a major feature of macrophages resulting in extreme heterogeneity both in normal and in pathological conditions. Macrophages are not homogenous, and they are generally categorized into two broad but distinct subsets as either classically activated (M1) or alternatively activated (M2). However, macrophages represent a continuum of highly plastic effector cells, resembling a spectrum of diverse phenotype states. Induction of specific macrophage functions is closely related to the surrounding environment that acts as a relevant orchestrator of macrophage functions. This phenomenon, termed polarization, results from cell/cell, cell/molecule interaction, governing macrophage functionality within the hosting tissues. Here, we summarized relevant cellular and molecular mechanisms driving macrophage polarization in "distant" pathological conditions, such as cancer, type 2 diabetes, atherosclerosis, and periodontitis that share macrophage-driven inflammation as a key feature, playing their dual role as killers (M1-like) and/or builders (M2-like). We also dissect the physio/pathological consequences related to macrophage polarization within selected chronic inflammatory diseases, placing polarized macrophages as a relevant hallmark, putative biomarkers, and possible target for prevention/therapy.

Cenicriviroc for the treatment of non-alcoholic steatohepatitis and liver fibrosis

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) has an increasing prevalence worldwide. At present, no specific pharmacotherapy is approved for NAFLD. Simple steatosis and nonalcoholic steatohepatitis (NASH) can progress to liver fibrosis that is associated with mortality in NAFLD. The recruitment of inflammatory monocytes and macrophages via chemokine receptor CCR2 as well as of lymphocytes and hepatic stellate cells via CCR5 promote the progression of NASH to fibrosis. Areas covered: I summarize preclinical and clinical data on the efficacy and safety of the dual CCR2/CCR5 inhibitor cenicriviroc (CVC, also TBR-652 or TAK-652) for the treatment of NASH and fibrosis. In animal models of liver diseases, CVC potently inhibits macrophage accumulation in the liver and ameliorates fibrosis. In a phase 2b clinical trial (CENTAUR) on 289 patients with NASH and fibrosis, CVC consistently demonstrated liver fibrosis improvement after 1 year of therapy and had an excellent safety profile, leading to the implementation of a phase 3 trial (AURORA). Expert opinion: Preclinical and clinical data support the development of CVC as a safe and potent antifibrotic agent. However, open questions around CVC are the durability of antifibrotic responses, divergent effects on NASH versus fibrosis, potential long-term concerns and the expected path to approval.

Selective targeting of tumor associated macrophages in different tumor models

Tumor progression largely depends on the presence of alternatively polarized (M2) tumor-associated macrophages (TAMs), whereas the classical M1-polarized macrophages can promote anti-tumorigenic immune responses. Thus, selective inhibition of M2-TAMs is a desirable anti-cancer approach in highly resistant tumor entities such as hepatocellular carcinoma (HCC) or breast cancer. We here examined whether a peptide that selectively binds to and is internalized by in vitro-differentiated murine M2 macrophages as compared to M1 macrophages, termed M2pep, could be used to selectively target TAMs in HCC and breast carcinoma. We confirmed selectivity of M2pep for in vitro M2 polarized macrophages. Upon incubation of suspended mixed 4T1 tumor cells with M2pep, high amounts of the TAMs were found to be associated with M2pep, whereas in mixed tumor cell suspensions from two HCC mouse models, M2pep showed only low-degree binding to TAMs. M2pep also showed low-degree targeting of liver macrophages. This indicates that the TAMs in different tumor entities show different targeting of M2pep and that M2pep is a very promising approach to develop selective M2-TAM-targeting in tumor entities containing M2-TAMs with significant amounts of the so far elusive M2pep receptor(s).

Myeloid cell heterogeneity in cancer: not a single cell alike

Tumors of various histological origins show abundant infiltration of myeloid cells from early stages of disease progression. These cells have a profound impact on antitumor immunity and influence fundamental processes that underlie malignancy, including neoangiogenesis, sustained cancer cell proliferation, metastasis and therapy resistance. For these reasons, development of therapeutic approaches to deplete or reprogram myeloid cells in cancer is an emerging field of interest. However, knowledge about the heterogeneity of myeloid cells in tumors and their variability between patients and disease stages is still limited. In this review, we summarize the most recent advances in our understanding about how the phenotype of tumor-associated macrophages, monocytes, neutrophils, myeloid-derived suppressor cells and dendritic cells is dictated by their ontogeny, activation status and localization. We also outline major open questions that will only be resolved by applying high-dimensional single-cell technologies and systems biology approaches in the analysis of the tumor microenvironment.

SPON2 Promotes M1-like Macrophage Recruitment and Inhibits Hepatocellular Carcinoma Metastasis by Distinct Integrin-Rho GTPase-Hippo Pathways

Tumor-associated macrophages (TAM) represent key regulators of the complex interplay between cancer and the immune microenvironment. Matricellular protein SPON2 is essential for recruiting lymphocytes and initiating immune responses. Recent studies have shown that SPON2 has complicated roles in cell migration and tumor progression. Here we report that, in the tumor microenvironment of hepatocellular carcinoma (HCC), SPON2 not only promotes infiltration of M1-like macrophages but also inhibits tumor metastasis. SPON2-α4β1 integrin signaling activated RhoA and Rac1, increased F-actin reorganization, and promoted M1-like macrophage recruitment. F-Actin accumulation also activated the Hippo pathway by suppressing LATS1 phosphorylation, promoting YAP nuclear translocation, and initiating downstream gene expression. However, SPON2-α5β1 integrin signaling inactivated RhoA and prevented F-actin assembly, thereby inhibiting HCC cell migration; the Hippo pathway was not noticeably involved in SPON2-mediated HCC cell migration. In HCC patients, SPON2 levels correlated positively with prognosis. Overall, our findings provide evidence that SPON2 is a critical factor in mediating the immune response against tumor cell growth and migration in HCC.Significance: Matricellular protein SPON2 acts as an HCC suppressor and utilizes distinct signaling events to perform dual functions in HCC microenvironment.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/9/2305/F1.large.jpg Cancer Res; 78(9); 2305-17. ©2018 AACR.

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.

Gut roundtable meeting paper: selected recent advances in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks number three among the most frequent causes of death from solid tumors worldwide. With obesity and fatty liver diseases as risk factors on the rise, HCC represents an ever increasing challenge. While there is still no curative treatment for most patients numerous novel drugs have been proposed, but most ultimately failed in phase III trials. This manuscript targets therapeutic advances and most burning issues. Expert key point summaries and urgent research agenda are provided regarding risk factors, including microbiota, need for prognostic and predictive biomarkers and the equivocal role of liver biopsy. Therapeutic topics highlighted are locoregional techniques, combination therapies and the potential of immunotherapy. Finally the manuscript provides a critical evaluation of novel targets and strategies for personalized treatment of HCC.

The immunology of hepatocellular carcinoma

In contrast to most other malignancies, hepatocellular carcinoma (HCC), which accounts for approximately 90% of primary liver cancers, arises almost exclusively in the setting of chronic inflammation. Irrespective of etiology, a typical sequence of chronic necroinflammation, compensatory liver regeneration, induction of liver fibrosis and subsequent cirrhosis often precedes hepatocarcinogenesis. The liver is a central immunomodulator that ensures organ and systemic protection while maintaining immunotolerance. Deregulation of this tightly controlled liver immunological network is a hallmark of chronic liver disease and HCC. Notably, immunotherapies have raised hope for the successful treatment of advanced HCC. Here we summarize the roles of specific immune cell subsets in chronic liver disease, with a focus on non-alcoholic steatohepatitis and HCC. We review new advances in immunotherapeutic approaches for the treatment of HCC and discuss the challenges posed by the immunotolerant hepatic environment and the dual roles of adaptive and innate immune cells in HCC.

Macrophage Polarization in Chronic Inflammatory Diseases: Killers or Builders?

Macrophages are key cellular components of the innate immunity, acting as the main player in the first-line defence against the pathogens and modulating homeostatic and inflammatory responses. Plasticity is a major feature of macrophages resulting in extreme heterogeneity both in normal and in pathological conditions. Macrophages are not homogenous, and they are generally categorized into two broad but distinct subsets as either classically activated (M1) or alternatively activated (M2). However, macrophages represent a continuum of highly plastic effector cells, resembling a spectrum of diverse phenotype states. Induction of specific macrophage functions is closely related to the surrounding environment that acts as a relevant orchestrator of macrophage functions. This phenomenon, termed polarization, results from cell/cell, cell/molecule interaction, governing macrophage functionality within the hosting tissues. Here, we summarized relevant cellular and molecular mechanisms driving macrophage polarization in “distant” pathological conditions, such as cancer, type 2 diabetes, atherosclerosis, and periodontitis that share macrophage-driven inflammation as a key feature, playing their dual role as killers (M1-like) and/or builders (M2-like). We also dissect the physio/pathological consequences related to macrophage polarization within selected chronic inflammatory diseases, placing polarized macrophages as a relevant hallmark, putative biomarkers, and possible target for prevention/therapy.

Monocytes/Macrophages promote vascular CXCR4 expression via the ERK pathway in hepatocellular carcinoma

We recently identified CXCR4 as a novel vascular marker for vessel sprouting in hepatocellular carcinoma (HCC) tissues. Thus, CXCR4⁺ endothelial cells (ECs) could serve as a potential predictor for patients who may benefit from sorafenib treatment; however, the mechanism that regulates vascular CXCR4 expression in HCC remains largely unknown. Here, we revealed a large number of monocytes/macrophages (Mo/Mϕ) to be selectively enriched in the perivascular areas of CXCR4⁺ vessels in HCC samples. The depletion of Mo/Mϕ with gadolinium chloride (GdCl₃) or zoledronic acid (ZA) treatment significantly reduced vascular CXCR4 expression in HCC tumors. This phenomenon was also confirmed in CCR2-KO mice, which exhibited reduced infiltration of inflammatory Mo/Mϕ in tumor tissues. Mechanistic studies revealed that inflammatory cytokines derived from tumor conditioned Mo/Mϕ, especially TNF-α, could up-regulate CXCR4 expression on ECs. TNF-α-induced activation of the Raf-ERK pathway, but not Notch signaling, was responsible for the expression of CXCR4. Moreover, the combination treatment of sorafenib with ZA was associated with improved anti-tumor efficacy by significantly reducing vascular CXCR4 expression. These findings revealed that Mo/Mϕ could regulate CXCR4 expression in the tumor vasculature. Thus, the inhibition of Mo/Mϕ inflammation might enhance the treatment efficacy of sorafenib in HCC.

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.

Inflammatory Monocytes Promote Perineural Invasion via CCL2-Mediated Recruitment and Cathepsin B Expression

Perineural invasion (PNI) is an ominous event strongly linked to poor clinical outcome. Cells residing within peripheral nerves collaborate with cancer cells to enable PNI, but the contributing conditions within the tumor microenvironment are not well understood. Here, we show that CCR2-expressing inflammatory monocytes (IM) are preferentially recruited to sites of PNI, where they differentiate into macrophages and potentiate nerve invasion through a cathepsin B-mediated process. A series of adoptive transfer experiments with genetically engineered donors and recipients demonstrated that IM recruitment to nerves was driven by CCL2 released from Schwann cells at the site of PNI, but not CCL7, an alternate ligand for CCR2. Interruption of either CCL2-CCR2 signaling or cathepsin B function significantly impaired PNI in vivo Correlative studies in human specimens demonstrated that cathepsin B-producing macrophages were enriched in invaded nerves, which was associated with increased local tumor recurrence. These findings deepen our understanding of PNI pathogenesis and illuminate how PNI is driven in part by corruption of a nerve repair program. Further, they support the exploration of inhibiting IM recruitment and function as a targeted therapy for PNI. Cancer Res; 77(22); 6400-14. ©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.

Long non-coding RNA HOTAIR up-regulates chemokine (C-C motif) ligand 2 and promotes proliferation of macrophages and myeloid-derived suppressor cells in hepatocellular carcinoma cell lines

Accumulating evidence demonstrated that Hox antisense intergenic RNA (HOTAIR) serves essential roles in the development and metastasis of several types of cancer. In hepatocellular carcinoma (HCC), high expression of HOTAIR is associated with poor prognosis, and HOTAIR regulates cell migration and proliferation. However, the downstream molecular targets of HOTAIR depend on the cancer cell types, and little is known about the precise molecular mechanisms of HOTAIR involved in cancer development. The present study investigated the role of HOTAIR in HCC cell lines. Notably, the overexpression of HOTAIR in HCC cell lines did not affect cell migration and proliferation capability. In the microarray analysis, C-C motif chemokine ligand (CCL)2 was identified to be differentially expressed in HOTAIR-overexpressing cells, and it was confirmed that HOTAIR promotes the secretion of CCL2. Furthermore, it was revealed that the proportion of macrophages and myeloid-derived suppressor cells (MDSCs) were increased when peripheral blood mononuclear cells were co-cultured with HOTAIR-overexpressing cells. Collectively, these data suggest that HOTAIR regulates CCL2 expression, which may be involved in the recruitment of macrophages and MDSCs to the tumor microenvironment.

Alternative splicing of hepatitis B virus: A novel virus/host interaction altering liver immunity

BACKGROUND & AIMS

Hepatitis B virus (HBV) RNA can undergo alternative splicing, but the relevance of this post-transcriptional regulation remains elusive. The mechanism of HBV alternative splicing regulation and its impact on liver pathogenesis were investigated.

METHODS

HBV RNA-interacting proteins were identified by RNA pull-down, combined with mass spectrometry analysis. HBV splicing regulation was investigated in chemically and surgically induced liver damage, in whole HBV genome transgenic mice and in hepatoma cells. Viral and endogenous gene expression were quantified by quantitative reverse transcription polymerase chain reaction, Western blot and enzyme-linked immunosorbent assay. Resident liver immune cells were studied by fluorescence-activated cell sorting.

RESULTS

HBV pregenomic RNA-interacting proteins were identified and 15% were directly related to the splicing machinery. Expression of these splicing factors was modulated in HBV transgenic mice with liver injuries and contributed to an increase of the HBV spliced RNA encoding for HBV splicing-generated protein (HBSP). HBSP transgenic mice with chemically induced liver fibrosis exhibited attenuated hepatic damage. The protective effect of HBSP resulted from a decrease of inflammatory monocyte/macrophage recruitment through downregulation of C-C motif chemokine ligand 2 (CCL2) expression in hepatocytes. In human hepatoma cells, the ability of HBSP to control CCL2 expression was confirmed and maintained in a whole HBV context. Finally, viral spliced RNA detection related to a decrease of CCL2 expression in the livers of HBV chronic carriers underscored this mechanism.

CONCLUSION

The microenvironment, modified by liver injury, increased HBSP RNA expression through splicing factor regulation, which in turn controlled hepatocyte chemokine synthesis. This feedback mechanism provides a novel insight into liver immunopathogenesis during HBV infection. Lay summary: Hepatitis B virus persists for decades in the liver of chronically infected patients. Immune escape is one of the main mechanisms developed by this virus to survive. Our study highlights how the crosstalk between virus and liver infected cells may contribute to this immune escape.

Nonresolving macrophage-mediated inflammation in malignancy

Tumors are populated with different cells of the immune system, each of which has the potential for pro- or antitumor functions. Macrophages are the numerically dominant type of myeloid cell in cancer and are suspected of having predominantly protumor functions. Key questions in cancer research concern the relationships between macrophages and anatomically different kinds of cancers, what specific properties of macrophages are involved in protumor functions and whether either macrophage numbers or functions can be modulated to enhance existing cancer therapies, for example, by reducing the immunosuppressive milieu such that anti-tumor T cells can provoke antitumor immunity. Accordingly, several antimacrophage preclinical modalities have been attempted and revealed substantial clinical barriers to their use. Therefore, understanding and targeting the specific pathways associated with protumor functions of macrophages, rather than macrophages themselves is a promising approach for both basic research and therapeutic development.

Differential impact of the dual CCR2/CCR5 inhibitor cenicriviroc on migration of monocyte and lymphocyte subsets in acute liver injury

A hallmark of acute hepatic injury is the recruitment of neutrophils, monocytes and lymphocytes, including natural killer (NK) or T cells, towards areas of inflammation. The recruitment of leukocytes from their reservoirs bone marrow or spleen into the liver is directed by chemokines such as CCL2 (for monocytes) and CCL5 (for lymphocytes). We herein elucidated the impact of chemokine receptor inhibition by the dual CCR2 and CCR5 inhibitor cenicriviroc (CVC) on the composition of myeloid and lymphoid immune cell populations in acute liver injury. CVC treatment effectively inhibited the migration of bone marrow monocytes and splenic lymphocytes (NK, CD4 T-cells) towards CCL2 or CCL5 in vitro. When liver injury was induced by an intraperitoneal injection of carbon tetrachloride (CCl₄) in mice, followed by repetitive oral application of CVC, flow cytometric and unbiased t-SNE analysis of intrahepatic leukocytes demonstrated that dual CCR2/CCR5 inhibition in vivo significantly decreased numbers of monocyte derived macrophages in acutely injured livers. CVC also reduced numbers of Kupffer cells (KC) or monocyte derived macrophages with a KC-like phenotype, respectively, after injury. In contrast to the inhibitory effects in vitro, CVC had no impact on the composition of hepatic lymphoid cell populations in vivo. Effective inhibition of monocyte recruitment was associated with reduced inflammatory macrophage markers and moderately ameliorated hepatic necroses at 36h after CCl₄. In conclusion, dual CCR2/CCR5 inhibition primarily translates into reduced monocyte recruitment in acute liver injury in vivo, suggesting that this strategy will be effective in reducing inflammatory macrophages in conditions of liver disease.

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.

A Natural CCR2 Antagonist Relieves Tumor-associated Macrophage-mediated Immunosuppression to Produce a Therapeutic Effect for Liver Cancer

Hepatocellular carcinoma (HCC) is a common malignant tumor in the digestive tract with limited therapeutic choices. Although sorafenib, an orally administered multikinase inhibitor, has produced survival benefits for patients with advanced HCC, favorable clinical outcomes are limited due to individual differences and resistance. The application of immunotherapy, a promising approach for HCC is urgently needed. Macrophage infiltration, mediated by the CCL2/CCR2 axis, is a potential immunotherapeutic target. Here, we report that a natural product from Abies georgei, named 747 and related in structure to kaempferol, exhibits sensitivity and selectivity as a CCR2 antagonist. The specificity of 747 on CCR2 was demonstrated via calcium flux, the binding domain of CCR2 was identified in an extracellular loop by chimera binding assay, and in vivo antagonistic activity of 747 was confirmed through a thioglycollate-induced peritonitis model. In animals, 747 elevated the number of CD8 + T cells in tumors via blocking tumor-infiltrating macrophage-mediated immunosuppression and inhibited orthotopic and subcutaneous tumor growth in a CD8 + T cell-dependent manner. Further, 747 enhanced the therapeutic efficacy of low-dose sorafenib without obvious toxicity, through elevating the numbers of intra-tumoral CD8 + T cells and increasing death of tumor cells. Thus, we have discovered a natural CCR2 antagonist and have provided a new perspective on development of this antagonist for treatment of HCC. In mouse models of HCC, 747 enhanced the tumor immunosuppressive microenvironment and potentiated the therapeutic effect of sorafenib, indicating that the combination of an immunomodulator with a chemotherapeutic drug could be a new approach for treating HCC.

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We identified a natural product, 747, as an antagonist of CCR2.

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747 exhibited anticancer properties and potentiated the efficacy of sorafenib in mouse models of HCC.

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A combination of immunotherapy and chemotherapy could be a new approach for treating HCC.

Hepatocellular carcinoma (HCC) is a common malignant tumor that arises in people with a chronic liver disorder and inflammation. Macrophage infiltration, controlled by the CCL2/CCR2 axis, is evident in various liver diseases, including hepatitis, cirrhosis, and tumor progression, making it a therapeutic immune target for liver cancer. In the present investigation, we identified a CCR2 antagonist, 747, from Abies georgei. In a mouse model of HCC, 747 alone exhibited anticancer properties and potentiated the antitumor efficacy of a low dose of sorafenib. Our findings indicate that a combination of immunotherapy and chemotherapy could be a new approach for treating HCC.

Peri-tumor associated fibroblasts promote intrahepatic metastasis of hepatocellular carcinoma by recruiting cancer stem cells

Fibroblasts have been reported to play an important role in hepatocellular carcinoma (HCC). However, the role of fibroblasts have not been fully understood. Conditioned medium collected from human peri-tumor tissue-derived fibroblasts (CM-pTAFs) showed high metastasis ability than human HCC tissues-derived fibroblasts (CM-TAFs). To determine what component was secreted from fibroblasts, we used Bio-Plex analysis system and compared the factors secreted from CM-pTAFs and CM-TAFs, found a series of up-regulated cytokines in the CM-pTAFs, including IL-6, CCL2, CXCL1, CXCL8, SCGF-β, HGF and VEGF. Pretreatment of IL-6 inhibitor Tocilizumab could inhibit metastasis the HCC cell treated with CM-pTAFs in vitro and in vivo. The expression of CCR2 and CXCR1 were up-regulated after CM-pTAFs treatment in HCC cell line SMMC-7721. Flow cytometric analysis experiment showed that most CCR2 or CXCR1 positive cells were also EpCAM positive. In vitro studies also showed that CM-pTAFs could increase stemness of SMMC-7721. In addition, neutralization of SCGF-β and HGF could significantly reduce metastasis and viability of cancer stem cells treated with CM-pTAFs. Taken together, these results indicated that the peri-tumor tissues derived fibroblasts may promote development of HCC by recruiting cancer stem cells and maintaining their stemness characteristic.

Mammary tumor-derived CCL2 enhances pro-metastatic systemic inflammation through upregulation of IL1β in tumor-associated macrophages

Patients with primary solid malignancies frequently exhibit signs of systemic inflammation. Notably, elevated levels of neutrophils and their associated soluble mediators are regularly observed in cancer patients, and correlate with reduced survival and increased metastasis formation. Recently, we demonstrated a mechanistic link between mammary tumor-induced IL17-producing γδ T cells, systemic expansion of immunosuppressive neutrophils and metastasis formation in a genetically engineered mouse model for invasive breast cancer. How tumors orchestrate this systemic inflammatory cascade to facilitate dissemination remains unclear. Here we show that activation of this cascade relies on CCL2-mediated induction of IL1β in tumor-associated macrophages. In line with these findings, expression of CCL2 positively correlates with IL1Β and macrophage markers in human breast tumors. We demonstrate that blockade of CCL2 in mammary tumor-bearing mice results in reduced IL17 production by γδ T cells, decreased neutrophil expansion and enhanced CD8⁺ T cell activity. These results highlight a new role for CCL2 in facilitating the breast cancer-induced pro-metastatic systemic inflammatory γδ T cell – IL17 – neutrophil axis.

Inflammation as target in cancer therapy

Cells of the innate immunity infiltrating tumour tissues promote, rather than halt, cancer cell proliferation and distant spreading. Tumour-Associated Macrophages (TAMs) are abundantly present in the tumour milieu and here trigger and perpetrate a state of chronic inflammation which ultimately supports disease development and contributes to an immune-suppressive environment. Therapeutic strategies to limit inflammatory cells and their products have been successful in pre-clinical tumour models. Early clinical trials with specific cytokine and chemokine inhibitors, or with strategies designed to target TAMs, are on their way in different solid malignancies. Partial clinical responses and stabilization of diseases were observed in some patients, in the absence of significant toxicity. These encouraging results open new perspectives of combination treatments aimed at reducing cancer-promoting inflammation to maximize the anti-tumour efficacy.