M2-like Tumor-associated Macrophages Polarization Research Articles

PCSK9 Suppresses M2-Like Tumor-Associated Macrophage Polarization by Regulating the Secretion of OX40L from Hepatocellular Carcinoma Cells

ABSTRACT Background Proprotein convertase subtilisin/kexin type 9 (PCSK9) participates in the development of various cancers, including hepatocellular carcinoma (HCC). Here, we attempted to reveal the underlying mechanism of PCSK9 in HCC. Methods Tumor tissues and adjacent tissues were separated from HCC patients to detect PCSK9 expression. Then, PCSK9 was overexpressed or silenced in HCC cells (MHCC97H or Huh7), and then the cell supernatant was incubated with THP-1 macrophages. OX40L neutralizing antibody (nAb) was used to inhibit OX40L activity. The expression of macrophage markers was examined by immunohistochemical staining and flow cytometry. Finally, tumor-bearing mouse model was constructed by inoculation of LV-PCSK9 infected MHCC97H cells to verify the role of PCSK in HCC. Results PCSK9 expression was decreased in tumor tissues of HCC patient specimens. HCC patients displayed M2 macrophage infiltration in tumor tissues. Moreover, PCSK9-silenced Huh7 cell supernatant promoted cell migration, and enhanced the proportion of CD206-positive cells and the expression of M2 macrophage markers IL-10 and ARG-1 in THP-1 macrophages. PCSK9-overexpressing MHCC97H cell supernatant inhibited THP-1 macrophage migration and M2-like tumor-associated macrophage (TAM) polarization, which was abolished by OX40L nAb treatment. PCSK9 overexpression enhanced the expression of OX40L in MHCC97H cells. In tumor-bearing mouse models, PCSK9 overexpression inhibited tumor growth and M2 polarization of TAMs in HCC by promoting OX40L expression. Conclusion: This work demonstrated that PCSK9 suppressed M2-like TAM polarization by regulating the secretion of OX40L from hepatocellular carcinoma cells. This study suggests that PCSK9 may be a potential target for HCC treatment.

RNA Sequencing Reveals Mechanisms Underlying Modulation of Hodgkin Lymphoma Cells and Tumor Microenvironment By the PI3K δ/γ Inhibitor, RP6530

INTRODUCTION: Aberrant activation of the phosphoinositide 3-kinase (PI3K) pathway plays a central role in Hodgkin Lymphoma (HL) pathogenesis. The pleiotropic activities of the δ and γ isoforms of PI3K in regulating the interactions of Hodgkin/Reed-Sternberg (HRS) cells with the tumor microenvironment suggest thatPI3K inhibitors might exert a therapeutic potential in the treatment of HL. The dual PI3K δ/γ inhibitor RP6530 was proven to affect HL tumor cells and to exert immunosuppressive activities. However, a genome-wide search for molecular mediators of RP6530 is largely unexplored in HL. The present study was therefore aimed at evaluating the anti-lymphoma functions and the underlying genes affected by RP6530 in HL cell lines.METHODS: We identified differentially expressed genes (DEGs) in two HL cell lines (L-540 and KM-H2) treated with RP6530 for 6 and 24 h by next generation RNA sequencing (RNA-Seq). The expression level of some of these genes was verified in HL cell lines using real time-PCR. Ingenuity Pathway Analysis (IPA) software was used to assign the DEGs to distinct canonical pathways and to predict the biological functions of the transcriptional changes. Gene silencing experiments were used to investigate and validate potential predictive biomarkers of response to RP6530 treatment. Additionally, serum levels of Thymus- and activation-regulated chemokine (TARC/CCL17) were analyzed by commercially available sandwich enzyme-linked immunosorbent assay (ELISA) in RP6530-treated HL patients enrolled in a phase 1 study.RESULTS: RNA-Seq analysis following treatment of L-540 cells for 6 h caused an upregulation of 1544 and downregulation of 839 genes. After a 24 h treatment period, 625 genes remained upregulated while the number of genes that were downregulated increased to 1362 (FDR ≤ 0.1). In KM-H2 cells, treatment with RP6530 for 6 or 24 h upregulated 137 and 980 genes while downregulating 139 and 833 genes, respectively (FDR ≤ 0.1). We further classified modulated genes according to their canonical pathways using the IPA suite. The most significantly upregulated pathways detected in both L-540 and KM-H2 cell lines included apoptosis, p53, death receptor signaling and G1/S cell cycle checkpoint regulation. In contrast, PI3K/AKT, ERK/MAPK, JAK/Stat, CD40, IL-4, IL-6, IL-10 and iNOS signaling were downregulated. We also identified 118 downregulated genes shared between the two cell lines that were associated with glycolysis, HIF1, chemokine and cytokine signaling. Upon RP6530 incubation, RNA-seq analysis showed a strikingly reduced expression of Pyruvate kinase muscle isozyme M2 (PKM2), which is a limiting glycolytic enzyme that catalyzes the final step in glycolysis. Here we show that lactic acid produced by tumor cells, as a by-product of glycolysis, has a critical function in inducing the M2-like polarization of tumor-associated macrophages (TAMs). Furthermore, we demonstrated that this effect was mediated by PKM2 and was inhibited after RP6530 treatment.We also found that the lactate-induced expression of M2 markers by macrophages, i.e., CCL-17 and CCL-22, were markedly inhibited both by RP6530 [-30% and -50% (mean of HL cells), respectively] and PKM2 silencing [-50% and -30% (mean of HL cells), respectively]. However, RP6530 increased the expression of M1 markers, switching the activation of macrophages from an immunosuppressive M2-like phenotype to an inflammatory M1-like state. PKM2 pathway therefore appears to be a critical determinant of RP6530-mediated inhibition of M2 macrophage polarization. Finally, RP6530 reduced the expression of key inflammation- and immunity-related genes as well as cytokines/chemokines and angiogenic factors (including, TARC/CCL17, CCL22, CCL5, IL-7, IL-13, and VEGF) known to be secreted by HRS cells to promote a pro-tumoral microenvironment. As the chemokine TARC/CCL17 is considered a biomarker of disease activity in HL patients, we observed a severe reduction of serum TARC/CCL17 levels in RP6530-treated HL patients that achieved CR or PR, but not in PD patients. Collectively, these findings suggest that RP6530 affects a mechanism of communication between HL tumor cells and tumor microenvironment.CONCLUSIONS: Results demonstrate that RP6530 can affect both HL tumor cells and HL tumor microenvironment, suggesting that a novel therapeutic opportunity may be achievable for the treatment of HL patients. DisclosuresViswanadha:Incozen Therapeutics: Employment. Vakkalanka:Rhizen Pharmaceuticals S A: Employment, Equity Ownership. Santoro:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees. Carlo-Stella:Boehringer Ingelheim: Consultancy, Honoraria; Rhizen Pharmaceuticals: Research Funding; ADC Therapeutics: Research Funding.

MiR-498 inhibits autophagy and M2-like polarization of tumor-associated macrophages in esophageal cancer via MDM2/ATF3.

Structured abstract Aim: To elucidate the effect of miRNA (miR)-498 on autophagy and M2-like macrophage polarization in esophageal cancer. Methods: Autophagy was evaluated in esophageal cancer. Macrophage markers specific for M1- or M2-like phenotype were determined. The binding relationships between miR-498 and MDM2, MDM2and ATF3 were analyzed. Results: miR-498 was downregulated in esophageal cancer and was associated with disease-free and overall patient survival. Enhanced miR-498 reduced LC3I conversion to LC3II and increased p62 accumulation in KYSE-150 cells, and increased macrophage polarization to M2-like phenotype in KYSE-150 and TAM co-culture. miR-498 inhibited MDM2-mediated ATF3 degradation, thus suppressing autophagy and M2-like polarization of macrophages in esophageal cancer. Conclusion: miR-498 may inhibit autophagy and M2-like polarization of macrophages to suppress esophageal cancer via MDM2/ATF3.

Sodium/glucose cotransporter 1-dependent metabolic alterations induce tamoxifen resistance in breast cancer by promoting macrophage M2 polarization

Endocrine therapy is the standard treatment for estrogen receptor (ER)-positive breast cancer, but tumors eventually develop resistance. However, endocrine therapy resistance mechanisms mediated through interactions between breast cancer cells and tumor-associated macrophages (TAMs) are still unclear. Here, we characterized sodium/glucose cotransporter 1 (SGLT1) overexpression drives the highly glycolytic phenotype of tamoxifen-resistant breast cancer cells where enhanced lactic acid secretion promotes M2-like TAM polarization via the hypoxia-inducible factor-1α/signal transducer and activator of transcription-3 pathway. In turn, M2-like TAMs activate breast cancer cells through EGFR/PI3K/Akt signaling, providing feedback to upregulate SGLT1 and promote tamoxifen resistance and accelerate tumor growth in vitro and in vivo. Higher expression of SGLT1 and CD163+ TAMs was associated with endocrine-resistant ER-positive breast cancers. Our study identifies a novel vicious cycle of metabolic reprogramming, M2-like TAM polarization, and endocrine therapy resistance, which involves SGLT1, proposing SGLT1 as a therapeutic target to overcome endocrine therapy resistance in breast cancer.

E3 ligase FBXW7 restricts M2-like tumor-associated macrophage polarization by targeting c-Myc.

FBXW7 functions as an E3 ubiquitin ligase to mediate oncoprotein degradation via the ubiquitin-proteasome system in cancer cells, effectively inhibiting the growth and survival of tumor cells. However, little is known about the functions of FBXW7 in macrophages and the tumor immune microenvironment. In this study, we find that FBXW7 suppresses M2-like tumor-associated macrophage (TAM) polarization to limit tumor progression. We identified a significant increase in the proportion of M2-like TAMs and aggravated tumor growth in mice with myeloid FBXW7 deficiency by subcutaneous inoculation with Lewis lung carcinoma cells (LLCs). When stimulated with LLCs supernatant in vitro, FBXW7-knockout macrophages displayed increased M2 macrophage polarization and enhanced ability of supporting cancer cells growth. In mechanism, we confirmed that FBXW7 inhibited M2-like TAM polarization by mediating c-Myc degradation via the ubiquitin-proteasome system. These findings highlight the role of FBXW7 in M2-like TAM polarization and provide new insights into the potential targets for cancer immunotherapies.

Blocking P2X7-Mediated Macrophage Polarization Overcomes Treatment Resistance in Lung Cancer.

P2X7, a crucial sensor of extracellular ATP, is widely distributed in different immune cells as a potent stimulant of inflammation and immunity. P2X7 is also highly expressed in immunosuppressive cells such as tumor-associated macrophages (TAM) and even tumor cells. However, the function and potential applications of P2X7-mediated immunosuppressive responses in the tumor microenvironment remain unclear. Here, we demonstrated that P2X7 was highly expressed in TAMs and that P2X7 deficiency impaired the "M2-like" polarization of TAMs via downregulation of STAT6 and IRF4 phosphorylation both in vivo and in vitro P2X7 deficiency restricted the progression of urethane-induced lung carcinogenesis and Lewis lung cancer by decreasing tumor cell proliferation and angiogenesis, promoting T-cell mobilization, and reversing M2-like TAM polarization. Thus, deletion or blockade of P2X7 was therapeutic for lung cancer. Furthermore, resistance to both immunotherapy (anti-PD-1 antibody) and chemotherapy (cisplatin) was overcome by coadministration of the P2X7 inhibitors O-ATP, A-438079 hydrochloride, and A-740003. Therefore, our data revealed a vital role of P2X7 in tumor formation through regulating TAM polarization, suggesting the therapeutic potential of P2X7 blockade in patients with lung cancer.

CPEB3 inhibits epithelial-mesenchymal transition by disrupting the crosstalk between colorectal cancer cells and tumor-associated macrophages via IL-6R/STAT3 signaling

BackgroundCrosstalk between cancer cells and tumor-associated macrophages (TAMs) mediates tumor progression in colorectal cancer (CRC). Cytoplasmic polyadenylation element binding protein 3 (CPEB3) has been shown to exhibit tumor-suppressive role in CRC.MethodsThe expression of CPEB3, CD68, CD86 and CD163 was determined in CRC tissues. SW480 or HCT116 cells overexpressing CPEB3 and LoVo or RKO cells with CPEB3 knockdown were constructed. Stably transfected CRC cells were co-cultured with THP-1 macrophages to determine the malignant phenotype of CRC cells, macrophage polarization, and secretory signals. The inhibition of CPEB3 on tumor progression and M2-like TAM polarization was confirmed in nude mice.ResultsDecreased CPEB3 expression in CRC was associated with fewer CD86+ TAMs and more CD163+ TAMs. CPEB3 knockdown in CRC cells increased the number of CD163+ TAMs and the expression of IL1RA, IL-6, IL-4 and IL-10 in TAM supernatants. TAMs enhanced CRC cell proliferation and invasion via IL-6, and then activated the IL-6R/STAT3 pathway in CRC cells. However, CPEB3 reduced the IL-6R protein levels by directly binding to IL-6R mRNA, leading to decreased phosphorylated-STAT3 expression in CRC cells. CCL2 was significantly increased in CPEB3 knockdown cells, while CCL2 antibody treatment rescued the effect of CPEB3 knockdown in promoting CD163+ TAM polarization. Eventually, we confirmed that CPEB3 inhibits tumor progression and M2-like TAM polarization in vivo.ConclusionsCPEB3 is involved in the crosstalk between CRC cells and TAMs by targeting IL-6R/STAT3 signaling.

ARS2/MAGL signaling in glioblastoma stem cells promotes self-renewal and M2-like polarization of tumor-associated macrophages

The interplay between glioblastoma stem cells (GSCs) and tumor-associated macrophages (TAMs) promotes progression of glioblastoma multiforme (GBM). However, the detailed molecular mechanisms underlying the relationship between these two cell types remain unclear. Here, we demonstrate that ARS2 (arsenite-resistance protein 2), a zinc finger protein that is essential for early mammalian development, plays critical roles in GSC maintenance and M2-like TAM polarization. ARS2 directly activates its novel transcriptional target MGLL, encoding monoacylglycerol lipase (MAGL), to regulate the self-renewal and tumorigenicity of GSCs through production of prostaglandin E2 (PGE2), which stimulates β-catenin activation of GSC and M2-like TAM polarization. We identify M2-like signature downregulated by which MAGL-specific inhibitor, JZL184, increased survival rate significantly in the mouse xenograft model by blocking PGE2 production. Taken together, our results suggest that blocking the interplay between GSCs and TAMs by targeting ARS2/MAGL signaling offers a potentially novel therapeutic option for GBM patients.

Zoledronic acid inhibits thyroid cancer stemness and metastasis by repressing M2-like tumor-associated macrophages induced Wnt/β-catenin pathway

AimsThis study aims to explore the effect and underlying mechanism of zoledronic acid (ZA) on the incidence of thyroid cancer (TC) tumorigenesis. Materials and methodsHuman mononuclear cells THP-1 were differentiated into M2-like tumor associated macrophages (TAMs) by incubation with PMA followed by additional incubation of IL-4 and IL-13. TC cells TPC-1 and IHH4 were co-cultured with M2-like TAMs. Identification of M2-like TAMs markers were determined by immunohistochemistry or flow cytometry. Cell proliferation, stemness and migration/invasion ability were measured by colony, sphere formation assay and transwell assay, respectively. The expression levels of cell stemness, EMT and Wnt/β-catenin pathway-related factors were verified by qRT-PCR, Western blotting, and immunofluorescence. A subcutaneous tumor model was established in nude mice to examine the in vivo effects of ZA. Key findingsM2-like TAMs were enriched in TC tissues, and they promoted the colony/sphere formation, accompanied with a down-regulated expression in E-cadherin and an up-regulated expression in N-cadherin, Vimentin and other stemness-associated markers (CD133, Oct4, c-Myc) in TC cells. The effects were suppressed when ZA co-treatment was given, because ZA inhibited the polarization of M2-like TAMs and β-catenin entry into the nucleus. Moreover, in agreement with in vitro data, ZA also limited subcutaneous tumor formation and macrophage enrichment in nude mice. SignificanceZA suppressed M2-like TAMs induced TC cell proliferation, stemness and metastasis through inhibiting M2-like TAMs polarization and Wnt/β-catenin pathway, which sheds light on the mechanisms of TC and provides avenues for the development of clinical therapy to TC.

CTHRC1 in Ovarian Cancer Promotes M2-Like Polarization of Tumor-Associated Macrophages via Regulation of the STAT6 Signaling Pathway.

PurposeThe infiltration of tumor-associated macrophages (TAMs) facilitates the progression of epithelial ovarian cancer (EOC). TAMs are mainly M2-like due to exposure to various factors in the tumor microenvironment. In our previous study, we reported that collagen triple helix repeat containing 1(CTHRC1), a secreted protein, is associated with ovarian cancer progression and metastasis. However, the correlation between CTHRC1 and the immunological microenvironment in EOC remains unknown.MethodsThe association with the expression of CTHRC1 and CD68+CD163+ TAMs infiltration density and phosphorylation of STAT6 was analyzed in tumor tissues of ovarian cancer patients by immunohistochemistry. Western blot and flow cytometry analysis were used to analyze M2-like macrophage polarization induced by CTHRC1. Cell Counting Kit-8 and adhesion assays were used to detect cell proliferation and adhesion, respectively. Cell migration and invasion were detected using transwell assays.ResultsIn the present study, we observed that the overexpression of CTHRC1 and increased TAMs infiltration density are closely correlated to an advanced stage of EOC. Meanwhile, CTHRC1 expression was positively associated with the infiltration density of M2-like CD68+CD163+TAMs and phosphorylation of STAT6 in EOC. In human PBMC-derived monocytes, recombinant CTHRC1 protein (rCTHRC1) induces an M2-like macrophage phenotype, in a dose-dependent manner, characterized by activating the STAT6 signaling pathway. The conditioned culture medium of Lenti-CTHRC1 EOC cells promoted M2 polarization of macrophages, and by contrast, CTHRC1 knockdown abolished STAT6-mediated M2 polarization of macrophages. Moreover, the culture supernatants of rCTHRC1-treated macrophages efficiently increased the migration and invasion abilities of ovarian cancer cells.ConclusionOur data indicate that CTHRC1 might play an important role in regulating M2 polarization of macrophages in the ovarian tumor microenvironment and suggest that it is a potential therapeutic target for antitumor immunity.

LncRNA RP11-361F15.2 promotes osteosarcoma tumorigenesis by inhibiting M2-Like polarization of tumor-associated macrophages of CPEB4.

Long non-coding RNAs (lncRNAs) regulates the initiation and progression of osteosarcoma (OS), specifically lncRNA RP11-361F15.2 has been shown to play prominent roles in tumorigenesis. Previously, M2-Like polarization of tumor-associated macrophages (TAMs) has been identified to play a key role in cancer migration/invasion. Hence, it is essential to understand the role of RP11-361F15.2 in tumorigenesis and its association with M2-Like polarization of TAMs. The results indicate that RP11-361F15.2 is significantly increased in OS tissues, and its expression is positively correlated with cytoplasmic polyadenylation element binding protein 4 (CPEB4) expression and negatively associated with miR-30c-5p expression. Further, overexpression of RP11-361F15.2 increased OS cell migration/invasion and M2-Like polarization of TAMs in vitro, as well as promoted xenograft tumor growth in vivo. Mechanistically, luciferase reporter assays indicated that RP11-361F15.2 upregulated CPEB4 expression by competitively binding to miR-30c-5p. Further, we have identified that RP11-361F15.2 promotes CPEB4-mediated tumorigenesis and M2-Like polarization of TAMs through miR-30c-5p in OS. We also identified that RP11-361F15.2 acts as competitive endogenous RNA (ceRNA) against miR-30c-5p thereby binding and activating CPEB4. This RP11-361F15.2/miR-30c-5p/CPEB4 loop could be used as a potential therapeutic strategy for the treatment of OS.

Aerobic glycolysis is a metabolic requirement to maintain the M2-like polarization of tumor-associated macrophages

Macrophages (MO) are versatile cells, assuming distinct functional phenotypes depending on the activating stimulus and the microenvironment. The differential activation of macrophages is supported by profound intracellular metabolic changes, being well accepted that the M1/M(LPS+IFN-γ) phenotype rely on aerobic glycolysis, while M2/M(IL-4) macrophages depend on oxidative metabolism. On the other hand, although tumor-associated macrophages (TAMs) are characterized by their high expression of M2/M(IL-4) markers, is currently unclear whether TAMs present the same oxidative metabolic profile of M2/M(IL-4) cells. Herein, we demonstrate for the first time that despite their high expression of M2/M(IL-4) markers, TAMs show high glycolytic activity, with high lactate secretion similar to the M1/M(LPS+ IFN-γ) phenotype. This activity seems to be essential for the M2 profile of TAMs, since the inhibition of glycolysis, but not the impairment of the oxidative phosphorylation or pentose phosphate pathway, diminished the expression of M2/M(IL-4) markers. These novel data indicate that TAMs, although are usually phenotyped as M2/M(IL-4)-like macrophages, they are metabolically distinct from these cells, being rather similar to M1/M(LPS+IFN-γ) macrophages, depending on the glycolytic metabolism to support their profile and functions.

RETRACTED ARTICLE: miR-195-5p/NOTCH2-mediated EMT modulates IL-4 secretion in colorectal cancer to affect M2-like TAM polarization

BackgroundTumor microenvironment (TME) is a complex environment containing tumor cells, tumor-associated macrophages (TAMs), interstitial cells, and non-cellular components. Epithelial–mesenchymal transition (EMT), as a major actor in cancer tumorigenicity and metastasis, was involved in the interaction between TAMs and tumor cells. However, the potential mechanisms of EMT and how EMT-programmed tumor cells affect M2-like TAMs still need further exploration.MethodsAn integrated analysis of nine CRC miRNA expression datasets was performed. Functional assays, including the EdU, clone formation, wound healing, and transwell assays, were used to determine the anticancer role of miR-195-5p in human CRC progression. Furthermore, RNA immunoprecipitation, RNA decay, and dual-luciferase reporter assays were used to determine the mechanism of miR-195-p CRC progression. Then co-culture, migration, and ELISA assays were applied to determine the role of miR-195-5p in macrophage recruitment and alternative polarization. Xenograft mouse models were used to determine the role of miR-195-5p in CRC tumorigenicity and TAM polarization in vivo.ResultsAn integrated analysis confirmed that miR-195-5p was significantly downregulated in CRC tissues, and patients with a low level of miR-195-5p had significantly shortened overall survival as revealed by the TCGA-COAD dataset. Altered miR-195-5p in colon cancer cells led to distinct changes of proliferation, migration, invasion, and EMT. Mechanistically, miR-195-5p regulated NOTCH2 expression in a post-transcriptional manner by directly binding to 3′-UTR of the Notch2 mRNA. Subsequently, miR-195-5p/NOTCH2 suppressed GATA3-mediated IL-4 secretion in CRC cells and ultimately inhibited M2-like TAM polarization.ConclusionsmiR-195-5p may play a vital role in regulating NOTCH2-mediated tumor cell EMT, thereby affecting IL-4-related M2-like TAM polarization in CRC.

Crosstalk between hepatic tumor cells and macrophages via Wnt/\u03b2-catenin signaling promotes M2-like macrophage polarization and reinforces tumor malignant behaviors

Tumor-associated macrophages (TAMs) are a major component of tumor microenvironment (TME) and play pivotal roles in the progression of hepatocellular carcinoma (HCC). Wnt signaling is evolutionarily conserved and participates in liver tumorigenesis. Several studies have shown that macrophage-derived Wnt ligands can activate Wnt signaling in tumor cells. However, whether Wnt ligands secreted by tumor cells can trigger Wnt signaling in macrophages is still elusive. In this study, we first verified that canonical Wnt/β-catenin signaling was activated during monocyte-to-macrophage differentiation and in M2-polarized macrophages. Knockdown of β-catenin in M2 macrophages exhibited stronger antitumor characteristics when cocultured with Hepa1-6 HCC cells in a series of experiments. Activation of Wnt signaling promoted M2 macrophage polarization through c-Myc. Moreover, co-culturing naïve macrophages with Hepa1-6 HCC cells in which Wnt ligands secretion was blocked by knockdown of Wntless inhibited M2 polarization in vitro. Consistently, the growth of HCC tumor orthotopically inoculated with Wntless-silenced Hepa1-6 cells was impeded, and the phenotype of M2-like TAMs was abrogated due to attenuated Wnt/β-catenin signaling in TAMs, leading to subverted immunosuppressive TME. Finally, we confirmed the correlation between M2 macrophage polarization and nuclear β-catenin accumulation in CD68+ macrophages in human HCC biopsies. Taken together, our study indicates that tumor cells-derived Wnt ligands stimulate M2-like polarization of TAMs via canonical Wnt/β-catenin signaling, which results in tumor growth, migration, metastasis, and immunosuppression in HCC. To block Wnts secretion from tumor cells and/or Wnt/β-catenin signal activation in TAMs may be potential strategy for HCC therapy in future.

Snail-overexpressing Cancer Cells Promote M2-Like Polarization of Tumor-Associated Macrophages by Delivering MiR-21-Abundant Exosomes

Epithelial-mesenchymal transition (EMT) is a major event during cancer progression and metastasis; however, the definitive role of EMT in remodeling tumor microenvironments (TMEs) is unclear. Tumor-associated macrophages (TAMs) are a major type of host immune cells in TMEs, and they perform a wide range of functions to regulate tumor colonization and progression by regulating tumor invasiveness, local tumor immunity, and angiogenesis. TAMs are considered to have an M2-like, i.e., alternatively activated, phenotype; however, how these EMT-undergoing cancer cells promote M2 polarization of TAMs as a crucial tumor-host interplay during cancer progression is unclear. In this study, we investigated the mechanism of EMT-mediated TAM activation. Here, we demonstrate that the EMT transcriptional factor Snail directly activates the transcription of MIR21 to produce miR-21-abundant tumor-derived exosomes (TEXs). The miR-21-containing exosomes were engulfed by CD14+ human monocytes, suppressing the expression of M1 markers and increasing that of M2 markers. Knockdown of miR-21 in Snail-expressing human head and neck cancer cells attenuated the Snail-induced M2 polarization, angiogenesis, and tumor growth. In head and neck cancer samples, a high expression of miR-21 was correlated with a higher level of SNAI1 and the M2 marker MRC1. This study elucidates the mechanism of EMT-mediated M2 polarization through delivery of the miR-21-abundant exosomes, which may serve as a candidate biomarker of tumor progression and provide a potential target for intercepting EMT-mediated TME remodeling.

Imatinib prevents lung cancer metastasis by inhibiting M2-like polarization of macrophages

Although M2-like tumor-associated macrophages (TAMs) have been considered as a vital therapeutic target in cancer therapy due to their role in promoting tumor progression and metastasis, very few compounds have been identified to inhibit M2-like polarization of TAMs. Here, we showed that Imatinib significantly prevented macrophage M2-like polarization induced by IL-13 or IL-4 in vitro, as illustrated by reduced expression of cell surface marker CD206 and M2-like genes, including Arg1, Mgl2, Mrc1, CDH1, and CCL2. Further, the migration of lung cancer cells promoted by the conditioned medium from M2-like macrophages could be restrained by Imatinib. Mechanistically, Imatinib inhibited STAT6 phosphorylation and nuclear translocation, resulting in the macrophage M2-like polarization arrest. Furthermore, Imatinib reduced the number of metastasis of Lewis lung cancer without affecting tumor growth. Both in tumor and lung tissues, the percentage of M2-like macrophages decreased after the administration of Imatinib for one week. Taken together, these data suggest that Imatinib is able to inhibit macrophage M2-like polarization, which plays a vital role in Imatinib suppressed metastasis of Lewis lung cancer.

Antitumor immunostimulatory activity of polysaccharides from Panax japonicus C. A. Mey: Roles of their effects on CD4 + T cells and tumor associated macrophages

In this study, chemical properties of polysaccharides from rhizomes of Panax japonicus C. A. Mey (PSPJ) were investigated and the antitumor immunostimulatory activity of PSPJ was assessed in mice bearing H22 hepatoma cells. Chemical properties of PSPJ were determined by GC, FT-IR, 1H NMR and 13C NMR analysis. Furthermore, we showed that PSPJ repressed H22 tumor growth in vivo with undetectable toxic effects on tumor-bearing mice. PSPJ upregulated host thymus/spleen indexes and ConA/LPS-induced splenocyte proliferation. Cytotoxic activities of natural killer and CD8+ T cells against H22 hepatoma cells were also elevated. Tumor transplantation led to substantial apoptosis of CD4+ T cells and dysregulation of the cytokine profile secreted by CD4+ T cells. These abnormalities were alleviated by PSPJ in a dose-dependent manner. In tumor-associated macrophages (TAMs), PSPJ reduced the production of immunosuppressive factors such as TGF-β, IL-10 and PEG2. In addition, M2-like polarization of TAMs was also considerably declined in response to PSPJ. Our findings clearly demonstrated the antitumor immunostimulatory activity of PSPJ and supported considering PSPJ as an adjuvant reagent in clinical treatment of malignant diseases.

Gefitinib inhibits M2-like polarization of tumor-associated macrophages in Lewis lung cancer by targeting the STAT6 signaling pathway.

M2-like polarized tumor-associated macrophages (TAMs) play a pivotal role in promoting cancer cell growth, invasion, metastasis and angiogenesis. The identification of M2-like TAMs during tumor progression is an attractive approach for cancer therapy. In this study, we investigated the relevance of macrophage polarization and the antitumor effect of gefitinib in Lewis Lung cancer (LLC) in vitro and in vivo. Gefitinib at a concentration below 2.5 μmol/L did not cause significant growth inhibition on LLC and RAW 264.7 cell lines and bone marrow-derived macrophage (BMDMs). However, a small concentration of gefitinib (0.62 μmol/L) significantly inhibited IL-13-induced M2-like polarization of macrophages, evidenced by the decreased expression of the M2 surface markers CD206 and CD163, down-regulation of specific M2-marker genes (Mrc1, Ym1, Fizz1, Arg1, IL-10 and CCL2) as well as inhibition of M2-like macrophage-mediated invasion and migration of LLC cells. In RAW 264.7 cells, gefitinib inhibits IL-13-induced phosphorylation of STAT6, which was a crucial signaling pathway in macrophage M2-like polarization. In LLC mice metastasis model, oral administration of gefitinib (75 mg·kg-1·d-1, for 21 d) significantly reduced the number of lung metastasis nodules, down-regulated the expression of M2 marker genes and the percentages CD206+ and CD68+ macrophages in tumor tissues. These results demonstrated that gefitinib effectively inhibits M2-like polarization both in vitro and in vivo, revealing a novel potential mechanism for the chemopreventative effect of gefitinib.

Regulated Polarization of Tumor-Associated Macrophages by miR-145 via Colorectal Cancer–Derived Extracellular Vesicles

Macrophages are polarized into functional classically activated and alternatively activated (M2) phenotypes depending on their microenvironment, and these cells play an important role in the immune system. M2-like polarization of tumor-associated macrophages (TAMs) is activated by various secretions from cancer cells; however, the interaction between cancer cells and TAMs is not well understood. Recent studies showed that cancer cell-derived extracellular vesicles (EVs) contribute to tumor development and modulation of the tumor microenvironment. In the current study, we investigated colorectal cancer-derived EVs containing miR-145 with respect to the polarization of TAMs. Colorectal cancer cells positively secreted miR-145 via EVs, which were taken up by macrophage-like cells. Interestingly, colorectal cancer-derived EVs polarized macrophage-like cells into the M2-like phenotype through the downregulation of histone deacetylase 11 An in vivo study showed that EV-treated macrophages caused significant enlargement of the tumor volumes. These findings suggest that colorectal cancer cells use miR-145 within EVs to efficiently modulate M2-like macrophage polarization and tumor progression.

Class A1 scavenger receptor modulates glioma progression by regulating M2-like tumor-associated macrophage polarization.

Macrophages enhance glioma development and progression by shaping the tumor microenvironment. Class A1 scavenger receptor (SR-A1), a pattern recognition receptor primarily expressed in macrophages, is up-regulated in many human solid tumors. We found that SR-A1 expression in 136 human gliomas was positively correlated with tumor grade (P<0.01), but not prognosis or tumor recurrence. SR-A1-expressing macrophages originated primarily from circulating monocytes attracted to tumor tissue, and were almost twice as numerous as resident microglia in glioma tissues (P<0.001). The effects of SR-A1 on glioma proliferation and invasion were assessed in vivo using an SR-A1-deficient murine orthotopic glioma model. SR-A1 deletion promoted M2-like tumor-associated macrophage (TAM) polarization in mice by activating STAT3 and STAT6, which resulted in robust orthotopic glioma proliferation and angiogenesis. Finally, we found that HSP70 might be an endogenous ligand that activates SR-A1-dependent anti-tumorigenic pathways in gliomas, although its expression does not appear informative for diagnostic purposes. Our findings demonstrate a relationship between TAMs, SR-A1 expression and glioma growth and provide new insights into the pathogenic role of TAMs in glioma.