M2-like Macrophage Polarization Research Articles

Multifunctional Ca2+ nanomodulators regulate type I interferon pathway to remodel tumor microenvironment for cancer immunotherapy

Although immune checkpoint blockade (ICB) therapy has been widely used for the treatment of a variety of cancers, its therapeutic efficacy is severely impaired by low tumor immunogenicity and the immunosuppressive microenvironment. Herein, we designed multifunctional immunomodulatory calcium nanoparticles to reshape the immunosuppressive tumor microenvironment. Our multifunctional calcium nanoparticles, CD@CaCO3P, are designed to release calcium ions and doxorubicin (DOX) into the acidic tumor microenvironment, which synergistically increase the tumor cell calcium ion concentration, while the release of combretastatin A4 phosphate (CA4P) further enhances T cell infiltration. Specifically, CD@CaCO3P effectively mediates the immunogenic cell death (ICD) of tumor cells and triggers the activation of nuclear factor kappa-B (NF-κB)/interferon regulatory factor 3 (IRF3), thereby regulating type I interferon (IFN-I) signaling pathways, and ultimately reprogramming the immunosuppressive tumor microenvironment by inducing M1-like macrophage polarization, promoting dendritic cell maturation, and increasing the infiltration of CD8+ T cells. Furthermore, CD@CaCO3P significantly increased tumor susceptibility to α-PD-1 checkpoint blocking immunotherapy and enhanced systemic immunotherapy performance against both primary and metastatic tumors. Our work provides new insights for the use functional calcium nanoparticles that modulate the tumor microenvironment to enhance the efficacy of cancer immunotherapy.

MiR-506 Promotes Antitumor Immune Response in Pancreatic Cancer by Reprogramming Tumor-Associated Macrophages toward an M1 Phenotype.

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant cancer with a poor prognosis, and effective treatments for PDAC are lacking. In this study, we hypothesized that miR-506 promotes antitumor immune response in PDAC by reprogramming tumor-associated macrophages toward an M1 phenotype to reverse its immunosuppressive tumor microenvironment (TME). First, the relationship between TME and the expression of miR-506 was assessed using clinical samples. Our results provided evidence that lower expression of miR-506 was associated with poor prognosis and immunosuppressive TME in PDAC patients. In addition, miR-506 inhibit the PDAC progression and reversed its immunosuppressive microenvironment in a macrophage-dependent manner. Next, we established a PDAC mouse model by orthotopic injection to further explore the role of miR-506 in vivo. Mechanistic investigations demonstrated that miR-506 could reprogram the polarization of M2-like macrophages toward an M1-like phenotype through targeting STAT3. Meanwhile, miR-506 could also sensitize PDAC to anti-PD-1 immunotherapy, because the tumor microenvironment remodeling effects of miR-506 could reprogram macrophage polarization and subsequently promote cytotoxic T lymphocyte (CTL) infiltration. These findings suggest a relationship between miR-506 and TME, especially M2-like macrophages, thus providing novel insights into mechanisms of tumor progression and potential immunotherapeutic targets for further clinical treatment.

SEMA4D/VEGF surface enhances endothelialization by diminished-glycolysis-mediated M2-like macrophage polarization

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammatory responses after percutaneous coronary intervention led to neoathrosclerosis and in-stent restenosis and thus increase the risk of adverse clinical outcomes. In this work, a metabolism reshaped surface is engineered, which combines the decreased glycolysis promoting, M2-like macrophage polarization, and rapid endothelialization property. Anionic heparin plays as a linker and mediates cationic SEMA4D and VEGF to graft electronically onto PLL surfaces. The system composed by anticoagulant heparin, immunoregulatory SEMA4D and angiogenic VEGF endows the scaffold with significant inhibition of platelets, fibrinogen and anti-thrombogenic properties, also noteworthy immunometabolism reprogram, anti-inflammation M2-like polarization and finally leading to rapid endothelializaiton performances. Our research indicates that the immunometabolism method can accurately reflect the immune state of modified surfaces. It is envisioned immunometabolism study will open an avenue to the surface engineering of vascular implants for better clinical outcomes.

Phagocytosis-initiated tumor hybrid cells acquire a c-Myc-mediated quasi-polarization state for immunoevasion and distant dissemination

While macrophage phagocytosis is an immune defense mechanism against invading cellular organisms, cancer cells expressing the CD47 ligand send forward signals to repel this engulfment. Here we report that the reverse signaling using CD47 as a receptor additionally enhances a pro-survival function of prostate cancer cells under phagocytic attack. Although low CD47-expressing cancer cells still allow phagocytosis, the reverse signaling delays the process, leading to incomplete digestion of the entrapped cells and subsequent tumor hybrid cell (THC) formation. Viable THCs acquire c-Myc from parental cancer cells to upregulate both M1- and M2-like macrophage polarization genes. Consequently, THCs imitating dual macrophage features can confound immunosurveillance, gaining survival advantage in the host. Furthermore, these cells intrinsically express low levels of androgen receptor and its targets, resembling an adenocarcinoma-immune subtype of metastatic castration-resistant prostate cancer. Therefore, phagocytosis-generated THCs may represent a potential target for treating the disease.

FBXO38 regulates macrophage polarization to control the development of cancer and colitis.

Macrophages are highly plastic cells that differentially regulate multiple pathological conditions, including cancer and autoimmune diseases. In response to various stimuli, macrophages activate different intrinsic signaling pathways and polarize into distinct macrophage subsets. We aimed to identify key new effectors that could control macrophage polarization and impact the development of cancer or colitis. Following treatment with the supernatants of tumor cells, macrophages showed an upregulation in Fbxo38 expression. Subsequently, we further identified that FBXO38 promotes macrophage immunosuppressive function by upregulating the expression of M2-like genes via MAPK and IRF4 signaling without affecting M1-like macrophage polarization. Deletion of Fbxo38 in macrophages was found to block tumor development and protect against DSS-induced colitis. Considering the distinct regulation of tumor development by FBXO38 in T cells and macrophages, we suggest that a comprehensive understanding of FBXO38 function in different cell types is critical for its further translational usage.

TIM-3 Expression and M2 Polarization of Macrophages in the TGFβ-Activated Tumor Microenvironment in Colorectal Cancer.

TGFβ signaling in the tumor microenvironment (TME) drives immune evasion and is a negative predictor of immune checkpoint inhibitor (ICI) efficacy in colorectal cancer (CRC). TIM-3, an inhibitory receptor implicated in anti-tumor immune responses and ICI resistance, has emerged as an immunotherapeutic target. This study investigated TIM-3, M2 macrophages and the TGFβ-activated TME, in association with microsatellite instability (MSI) status and consensus molecular subtypes (CMSs). Transcriptomic cohorts of CRC tissues, organoids and xenografts were examined (n = 2240). TIM-3 and a TGFβ-inducible stromal protein, VCAN, were evaluated in CRC specimens using immunohistochemistry (n = 45). TIM-3 expression on monocytes and generated M2 macrophages was examined by flow cytometry. We found that the expression of HAVCR2 (TIM-3) significantly correlated with the transcriptional signatures of TGFβ, TGFβ-dependent stromal activation and M2 macrophage, each of which were co-upregulated in CMS4, CMS1 and MSI CRCs across all datasets. Tumor-infiltrating TIM-3+ immune cells accumulated in TGFβ-responsive cancer stroma. TIM-3 was increased on M2-polarized macrophages, and on monocytes in response to TGFβ treatment. In conclusion, we identified a close association between TIM-3 and M2-like polarization of macrophages in the TGFβ-rich TME. Our findings provide new insights into personalized immunotherapeutic strategies based on the TME for CRCs.

Lapachol inhibits the growth of lung cancer by reversing M2-like macrophage polarization via activating NF-κB signaling pathway

Resetting tumor-associated macrophages (TAMs) is a promising strategy to ameliorate the immunosuppressive tumor microenvironment (TME) and improve innate and adaptive antitumor immunity. Lapachol, a naturally occurring 1,4-naphthoquinone, exhibits various pharmacological activities including antitumor, anti-leishmanial, antimalarial and antiseptic. In this study, we investigated the relevance of macrophage polarization and the antitumor effect of lapachol in Lewis lung cancer (LLC) both in vitro and in vivo. This study demonstrated that lapachol significantly reversed the polarization of M2-like macrophages thus that were endowed with the ability to kill LLC cells by activating NF-κB signaling pathway. Furthermore, lapachol effectively suppressed tumor growth in C57BL/6 mice bearing lung tumors by reducing the proportion of M2-like macrophages. Overall, our findings clearly illustrated that lapachol could reverse the polarization of M2-like macrophages to improve the immunosuppressive tumor microenvironment, and had the potential to be developed as an immunomodulatory antitumor agent.

BPIFB1 promotes metastasis of hormone receptor-positive breast cancer via inducing macrophage M2-like polarization.

Metastasis is an important factor affecting the prognosis of hormone receptor-positive breast cancer (BC). However, the molecular basis for migration and invasion of tumor cells remains poorly understood. Here, we identify that bactericidal/permeability-increasing-fold-containing family B member 1 (BPIFB1), which plays an important role in innate immunity, is significantly elevated in breast cancer and associated with lymph node metastasis. High expression of BPIFB1 and its coding mRNA are significantly associated with poor prognosis of hormone receptor-positive BC. Using enrichment analysis and constructing immune infiltration evaluation, we predict the potential ability of BPIFB1 to promote macrophage M2 polarization. Finally, we demonstrate that BPIFB1 promotes the metastasis of hormone receptor-positive BC by stimulating the M2-like polarization of macrophages via the establishment of BC tumor cells/THP1 co-culture system, qPCR, Transwell assay, and animal experiments. To our knowledge, this is the first report on the role of BPIFB1 as a tumor promoter by activating the macrophage M2 polarization in hormone receptor-positive breast carcinoma. Together, these results provide novel insights into the mechanism of BPIFB1 in BC.

Targeted inhibition of eIF5Ahpu suppresses tumor growth and polarization of M2-like tumor-associated macrophages in oral cancer

Eukaryotic initiation factor 5A2 (eIF5A2) is overexpressed in many types of cancer, and spermidine-mediated eIF5A hypusination (eIF5Ahpu) appears to be essential to most of eIF5A’s biological functions, including its important role in regulating cancer cell proliferation, epithelial–mesenchymal transition (EMT), and cancer stem cell (CSC) properties as well as immune cell functions. Here we investigated the role of eIF5Ahpu in the growth of oral squamous cell carcinoma cells (OSCCs) and OSCC-induced polarization of M2-like tumor-associated macrophages (TAMs). TCGA dataset analysis revealed an overall upregulation in the mRNA expression of eIF5A2 and several key enzymes involved in polyamine (PA) metabolism in HNSCC, which was confirmed by Western blot and IHC studies. Blocking eIF5Ahpu by GC-7 but not the upstream key enzyme activities of PA metabolism, remarkably inhibited cell proliferation and the expression of EMT- and CSC-related genes in OSCC cells. In addition, blocking eIF5Ahpu robustly inhibited OSCC-induced M2-like TAM polarization in vitro. More Importantly, blocking eIF5Ahpu dramatically retarded tumor growth and infiltration/polarization of M2-like TAM in a syngeneic orthotopic murine tongue SCC model. Thus, eIF5Ahpu plays dual functions in regulating tumor cell growth and polarization of M2-TAMs in OSCC.

Dose-related immunomodulatory effects of recombinant TRAIL in the tumor immune microenvironment

BackgroundIn addition to specifically inducing tumor cell apoptosis, recombinant tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has also been reported to influence the cancer immune microenvironment; however, its underlying effects and mechanisms remain unclear. Investigating the immunomodulatory effects and mechanisms of recombinant TRAIL in the tumor microenvironment (TME) may provide an important perspective and facilitate the exploration of novel TRAIL strategies for tumor therapy.MethodsImmunocompetent mice with different tumors were treated with three doses of recombinant TRAIL, and then the tumors were collected for immunological detection and mechanistic investigation. Methodological approaches include flow cytometry analysis and single-cell sequencing.ResultsIn an immunocompetent mouse model, recombinant soluble mouse TRAIL (smTRAIL) had dose-related immunomodulatory effects. The optimal dose of smTRAIL (2 mg/kg) activated innate immune cells and CD8+ T cells, whereas higher doses of smTRAIL (8 mg/kg) promoted the formation of a tumor-promoting immune microenvironment to counteract the apoptotic effects on tumor cells. The higher doses of smTRAIL treatment promoted M2-like macrophage recruitment and polarization and increased the production of protumor inflammatory cytokines, such as IL-10, which deepened the suppression of natural killer (NK) cells and CD8+ T cells in the tumor microenvironment. By constructing an HU-HSC-NPG.GM3 humanized immune system mouse model, we further verified the immunomodulatory effects induced by recombinant soluble human TRAIL (shTRAIL) and found that combinational administration of shTRAIL and trabectedin, a macrophage-targeting drug, could remodel the tumor immune microenvironment, further enhance antitumor immunity, and strikingly improve antitumor effects.ConclusionOur results highlight the immunomodulatory role of recombinant TRAIL and suggest promising therapeutic strategies for clinical application.Graphical

Pentraxin 3 deficiency ameliorates the severity of osteoarthritis and alleviates inflammation

BackgroundOsteoarthritis is one of the most common degenerative joint disorders, characterized by articular cartilage breakdown, synovitis, osteophytes generation and subchondral bone sclerosis. Pentraxin 3 (PTX3) is a long pentraxin protein, secreted by immune cells, and PTX3 is identified to play a critical role in inflammation and macrophage polarization. However, the underlying mechanism of PTX3 in osteoarthritis under the circumstance of Ptx3-knockout (KO) mice model is still unknown. MethodsMurine destabilization of the medial meniscus (DMM) OA model was created in Ptx3-knockout (KO) and wildtype mice, respectively. The degenerative status of cartilage was detected by Safranin O, H&E staining, immunohistochemistry (IHC) and micro-CT. OARSI scoring was employed to assess the proteoglycan of cartilage. Serum inflammatory cytokines were examined by ELISA and systematic macrophage polarization in spleen was analyzed by flow cytometry. ResultsSafranin O and H&E staining confirmed that the joint cartilage was mostly with reduced degeneration in both the senior KO mice and the DMM model generated from the KO mice, compared to the WT group. This is also supported by micro-CT examination and OARSI scoring. Immunohistochemistry illustrated an up-regulation of Aggrecan and Collagen 2 and down-regulation of ADAMTS-5 and MMP13 in KO mice in comparison with the WT mice. ELISA indicated a dramatical decrease in the serum levels of TNF-α and IL-6 in KO mice. Polarization of M2-like macrophages was observed in the KO group. ConclusionPentraxin 3 deficiency significantly ameliorated the severity of osteoarthritis by preventing cartilage degeneration and alleviated systematic inflammation by inducing M2 polarization.

Ezh2 emerges as an epigenetic checkpoint regulator during monocyte differentiation limiting cardiac dysfunction post-MI

Epigenetic regulation of histone H3K27 methylation has recently emerged as a key step during alternative immunoregulatory M2-like macrophage polarization; known to impact cardiac repair after Myocardial Infarction (MI). We hypothesized that EZH2, responsible for H3K27 methylation, could act as an epigenetic checkpoint regulator during this process. We demonstrate for the first time an ectopic EZH2, and putative, cytoplasmic inactive localization of the epigenetic enzyme, during monocyte differentiation into M2 macrophages in vitro as well as in immunomodulatory cardiac macrophages in vivo in the post-MI acute inflammatory phase. Moreover, we show that pharmacological EZH2 inhibition, with GSK-343, resolves H3K27 methylation of bivalent gene promoters, thus enhancing their expression to promote human monocyte repair functions. In line with this protective effect, GSK-343 treatment accelerated cardiac inflammatory resolution preventing infarct expansion and subsequent cardiac dysfunction in female mice post-MI in vivo. In conclusion, our study reveals that pharmacological epigenetic modulation of cardiac-infiltrating immune cells may hold promise to limit adverse cardiac remodeling after MI.

Autophagy suppression facilitates macrophage M2 polarization via increased instability of NF-κB pathway in hepatocellular carcinoma

The tumor microenvironment is a highly heterogeneous circumstance composed of multiple components, while tumor-associated macrophages (TAMs) are major innate immune cells with highly plastic and are always educated by tumor cells to structure an advantageous pro-tumor immune microenvironment. Despite emerging evidence focalizing the role of autophagy in other immune cells, the regulatory mechanism of autophagy in macrophage polarization remains poorly understood. Herein, we demonstrated that hepatocellular carcinoma (HCC) cells educated macrophages toward M2-like phenotype polarization under the condition of coculture. Moreover, we observed that inhibition of macrophage autophagy promoted M2-like macrophage polarization, while the tendency was impeded when autophagy was motivated. Mechanistically, macrophage autophagy inhibition inactivates the NF-κB pathway by increasing the instability of TAB3 via ubiquitination degradation, which leads to the M2-like phenotype polarization of macrophages. Both immunohistochemistry staining using human HCC tissues and experiment in vivo verified autophagy inhibition is correlated with M2 macrophage polarization. Altogether, we illustrated that macrophage autophagy was involved in the process of HCC cells domesticating M2 macrophage polarization via the NF-κB pathway. These results provide a new target to interfere with the polarization of macrophages to M2-like phenotype during HCC progression.

Adoptive transfer of Fe3O4-SWCNT engineered M1-like macrophages for magnetic resonance imaging and enhanced cancer immunotherapy

Macrophage-based tumor immunotherapy can effectively kill tumor cells in a direct manner when tumor specific antigens are idle or unknown. However, the presence of M2-like tumor associated macrophages (TAMs) would limit the treatment efficiency. Therefore, reversing the M2-like TAMs phenotype to regulate the immunosuppressive tumor microenvironment (TME) is crucial. Herein, we proposed nano-sized ferroferric oxide/single wall carbon nanotubes composites (Fe3O4-SWCNT) to engineer the macrophages species for powerful cancer therapy. The synthesized Fe3O4-SWCNT revealed good magnetic resonance imaging (MRI) performance, which enabled in vivo tracking of macrophage mediated immunotherapy. In addition, Fe3O4-SWCNT engineered M1-like macrophages (Fe3O4-SWCNT@M1) could maintain M1 phenotype, migrate to tumor cells and release nitric oxide (NO), reactive oxygen species (ROS) and tumor necrosis factor-α (TNF-α). A series of experimental results showed that Fe3O4-SWCNT@M1 could effectively promote the polarization of endogenous M2-like macrophages to M1-like macrophages, activate tumor immune response and inhibit tumor progression. This work is expected to provide a new vision for macrophage-based tumor immunotherapy.

Gremlin 1 is required for macrophage M2 polarization.

Pro-proliferative, M2-like polarization of macrophages is a critical step in the development of fibrosis and remodeling in chronic lung diseases such as pulmonary fibrosis and pulmonary hypertension. Macrophages in healthy and diseased lungs express gremlin 1 (Grem1), a secreted glycoprotein that acts in both paracrine and autocrine manners to modulate cellular function. Increased Grem1 expression plays a central role in pulmonary fibrosis and remodeling, however, the role of Grem1 in M2-like polarization of macrophages has not previously been explored. The results reported here show that recombinant Grem1 potentiated M2-like polarization of mouse macrophages and bone marrow-derived macrophages (BMDMs) in response to the Th2 cytokines IL4 and IL13. Genetic depletion of Grem1 in BMDMs inhibited M2 polarization while exogenous gremlin 1 could partially rescue this effect. Taken together, these findings reveal that gremlin 1 is required for M2-like polarization of macrophages.NEW & NOTEWORTHY We show here that gremlin 1 potentiated M2 polarization of mouse bone marrow-derived macrophages (BMDMs) in response to the Th2 cytokines IL4 and IL13. Genetic depletion of Grem1 in BMDMs inhibited M2 polarization while exogenous gremlin 1 partially rescued this effect. Taken together, these findings reveal a previously unknown requirement for gremlin 1 in M2 polarization of macrophages and suggest a novel cellular mechanism promoting fibrosis and remodeling in lung diseases.

Exosomal miR-6733-5p mediates cross-talk between glioblastoma stem cells and macrophages and promotes glioblastoma multiform progression synergistically.

Exosomal miRNAs derived from glioblastoma stem cells (GSCs) are important mediators of immunosuppressive microenvironment formation in glioblastoma multiform (GBM), especially in M2-like polarization of tumor-associated macrophages (TAMs). However, the exact mechanisms by which GSCs-derived exosomes (GSCs-exo) facilitate the remodeling of the immunosuppressive microenvironment of GBM have not been elucidated. Transmission electron microscopy (TME) and nanoparticle tracking analysis (NTA) were applied to verify the existence of GSCs-derived exosomes. Sphere formation assays, flow cytometry, and tumor xenograft transplantation assays were performed to identify the exact roles of exosomal miR-6733-5p. Then, the mechanisms of miR-6733-5p and its downstream target gene regulating crosstalk between GSCs cells and M2 macrophages were further investigated. GSCs-derived exosomal miR-6733-5p induce macrophage M2 polarization of TAMs by positively targeting IGF2BP3 to activate the AKT signaling pathway, which further facilitates the self-renewal and stemness of GSCs. GSCs secrete miR-6733-5p-rich exosomes to induce M2-like polarization of macrophages, as well as enhance GSCs stemness and promote malignant behaviors of GBM through IGF2BP3 activated AKT pathway. Targeting GSCs exosomal miR-6733-5p may provide a potential new strategy against GBM.

MiR-141-3p accelerates ovarian cancer progression and promotes M2-like macrophage polarization by targeting the Keap1-Nrf2 pathway.

The miR-141-3p has been reported to participate in regulating autophagy and tumor-stroma interactions in ovarian cancer (OC). We aim to investigate whether miR-141-3p accelerates the progression of OC and its effect on macrophage 2 polarization by targeting the Kelch-like ECH-associated protein1-Nuclear factor E2-related factor2 (Keap1-Nrf2) pathway. SKOV3 and A2780 cells were transfected with miR-141-3p inhibitor and negative control to confirm the regulation of miR-141-3p on OC development. Moreover, the growth of tumors in xenograft nude mice treated by cells transfected with miR-141-3p inhibitor was established to further testify the role of miR-141-3p in OC. The expression of miR-141-3p was higher in OC tissue compared with non-cancerous tissue. Downregulation of miR-141-3p inhibited the proliferation, migration, and invasion of ovarian cells. Furthermore, miR-141-3p inhibition also suppressed M2-like macrophage polarization and in vivo OC progression. Inhibition of miR-141-3p significantly enhanced the expression of Keap1, the target gene of miR-141-3p, and thus downregulated Nrf2, while activation of Nrf2 reversed the reduction in M2 polarization by miR-141-3p inhibitor. Collectively, miR-141-3p contributes to tumor progression, migration, and M2 polarization of OC by activating the Keap1-Nrf2 pathway. Inhibition of miR-141-3p attenuates the malignant biological behavior of ovarian cells by inactivating the Keap1-Nrf2 pathway.

Tumor-Specific Peroxynitrite Overproduction Disrupts Metabolic Homeostasis for Sensitizing Melanoma Immunotherapy.

Tumor cells elicit metabolic reprogramming to establish an immunosuppressive tumor microenvironment (TME) for escaping from immunosurveillance. Therefore, interrupting the metabolic adaption of tumor cells might be a promising strategy for TME immunomodulation, favoring immunotherapy. Herein, w e construct a tumor-specific ONOO- nanogenerator (APAP-P-NO) that can selectively disrupt metabolic homeostasis in melanoma cells. Stimulated by melanoma-characteristic acid, glutathione, and tyrosinase, APAP-P-NO could efficiently generate ONOO- through the in situ coupling of the produced O2 •- and released NO. Metabolomics profiling reveals that the accumulated ONOO- induces great decrease of metabolites involved in the TCA cycle. Meanwhile, the aerobic glycolysis-produced lactate drops sharply both intracellularly and extracellularly under ONOO- stress. Mechanistically, ONOO- impairs the activity of glyceraldehyde-3-phosphate dehydrogenase in glucose metabolism through S-nitrosylation. The metabolic alterations effectively reverse the immunosuppressive TME to evoke potent antitumor immune responses, including polarization of M2-like macrophages to M1 phenotype, reduction of myeloid-derived suppressor cells and regulatory T cells, and restoration of CD8+ T cell infiltration. Combining APAP-P-NO pretreatment with anti-PD-L1 achieves a significant inhibition against both primary and metastatic melanomas without systemic toxicities. Collectively, w e develop a tumor-specific ONOO- overproduction approach and explore the possible mechanism of ONOO- -mediated TME immunomodulation, providing a new strategy for facilitating immunotherapy sensitivity. This article is protected by copyright. All rights reserved.

Garcinone E suppresses breast cancer growth and metastasis by modulating tumor-associated macrophages polarization via STAT6 signaling.

Cancer metastasis remains the most common cause of death in breast cancer patients. Tumor-associated macrophages (TAMs) are a novel therapeutic target for the treatment of metastatic breast cancer. Despite the good anti-cancer activity of garcinone E (GE), there are no reports on its therapeutic effects on breast cancer metastasis. The objective of this study was to examine the anti-cancer effects of GE on metastatic breast cancer. RAW 264.7 and THP-1 cells were polarized to M2 macrophages by IL-4/IL-13 in vitro. A 4T1 mouse breast cancer model and the tail vein breast cancer metastasis model were used to explore the effect of GE on breast cancer growth and metastasis in vivo. In vitro studies showed that GE dose-dependently suppressed IL-4 + IL-13-induced expression of CD206 in both RAW 264.7 cells and differentiated THP-1 macrophages. However, GE did not affect the LPS + IFN-γ-induced polarization to the M1-like macrophages in vitro. GE inhibited the expression of the M2 macrophage specific genes in RAW 264.7 cells, and simultaneously impaired M2 macrophage-induced breast cancer cell proliferation and migration, and angiogenesis. In animal studies, GE significantly suppressed tumor growth, angiogenesis, and lung metastasis in 4T1 tumor-bearing mice, without causing toxicity. In both tumor and lung tissues, the proportion of M2-like TAMs was significantly decreased while the proportion of M1-like TAMs was markedly increased by GE treatment. Mechanistically, GE inhibited phosphorylation of STAT6 in vitro and in vivo. Our results demonstrate for the first time that GE suppresses breast cancer growth and pulmonary metastasis by modulating M2-like macrophage polarization through the STAT6 signaling pathway.

Mesenchymal Stromal Cell Exosomes Mediate M2-like Macrophage Polarization through CD73/Ecto-5'-Nucleotidase Activity.

Mesenchymal stem/stromal cell (MSC) exosomes have been shown to alleviate immune dysfunction and inflammation in preclinical animal models. This therapeutic effect is attributed, in part, to their ability to promote the polarization of anti-inflammatory M2-like macrophages. One polarization mechanism has been shown to involve the activation of the MyD88-mediated toll-like receptor (TLR) signaling pathway by the presence of extra domain A-fibronectin (EDA-FN) within the MSC exosomes. Here, we uncovered an additional mechanism where MSC exosomes mediate M2-like macrophage polarization through exosomal CD73 activity. Specifically, we observed that polarization of M2-like macrophages by MSC exosomes was abolished in the presence of inhibitors of CD73 activity, adenosine receptors A2A and A2B, and AKT/ERK phosphorylation. These findings suggest that MSC exosomes promote M2-like macrophage polarization by catalyzing the production of adenosine, which then binds to adenosine receptors A2A and A2B to activate AKT/ERK-dependent signaling pathways. Thus, CD73 represents an additional critical attribute of MSC exosomes in mediating M2-like macrophage polarization. These findings have implications for predicting the immunomodulatory potency of MSC exosome preparations.