Migrating Type 2 Dendritic Cells Prime Mucosal Th17 Cells Specific to Small Intestinal Commensal Bacteria

Dendritic cells (DCs) are professional APCs equipped with MHC-restricted Ags, costimulations, and cytokines that effectively prime and differentiate naive T cells into distinct functional subsets. The immune signals that DCs carry reflect the route of Ag uptake and the innate stimuli they received. In the mucosal tissues, owing to the great variety of foreign Ags and inflammatory cues, DCs are predominantly activated and migratory. In the small intestine, CD4 Th17 cells are abundant and have been shown to be regulated by DCs and macrophages. Using a mouse commensal bacteria experimental model, we identified that the early priming step of commensal-driven Th17 cells is controlled by bona fide Zbtb46-expressing DCs. CCR7-dependent migration of type 2 DCs (DC2s) from the small intestine to the mesenteric lymph nodes (MLNs) is essential for the activation of naive CD4 T cells. The migratory DC2 population in the MLNs is almost exclusively Esam+ cells. Single-cell RNA sequencing highlighted the abundance of costimulatory markers (CD40 and OX40) and chemokines (Ccl22 and Cxcl16) on MLN migratory DCs. Further resolution of MLN migratory DC2s revealed that the Th17-polarizing cytokine IL-6 colocalizes with DC2s expressing CD40, Ccl17, and Ccl22. Thus, early Th17 cell differentiation is initiated by a small subset of migratory DC2s in the gut-draining lymph nodes.

Molecular chaperone GP96 is a potential target to modulate dendritic cell programming and shape anti-tumor immunity

Dendritic cells (DCs) are professional antigen-presenting cells providing costimulatory signals to adaptive immune cells. Currently, the lack of strategies to improve antigen presentation is a hindrance in tumor immunology. Despite studies focusing on antigen cross-presenting Type-1 DCs (DC1s), a study published by our lab revealed Type-2 DCs (DC2s) with significant survival across multiple human cancers. Our research group has a long-term interest in studying immune chaperone GP96, which is an essential molecular chaperone for TLRs, GARP, and other vital innate receptors. The immune-related client network of GP96 creates opportunities to unmask the roles of multiple receptors on DCs. We have generated DC-specific GP96 deficient mice and reported increased tumor-infiltrating DC2 and delayed tumor development on the spontaneous breast cancer model. However, the mechanism by which GP96 regulates DCs function is under investigation. Using different tumor models, we found that deletion of GP96 on DCs improved immune response and decreased tumor growth. However, macrophage-GP96KO mice showed a loss of benefits observed on DC-GP96KO mice. Also, differential stimulatory/inhibitory molecules on DC1 vs. DC2 were tumor-dependent. To determine the role of DC-intrinsic GP96 in T cell activation, we used in vitro antigen-cross presentation assay. We found that OT-I CD8+ T cell activation was delayed at the initial days of the co-culture with GP96KO DCs but restored in the late phase compared with WT DCs. Collectively, the results show beneficial inflammatory DC2 molecular activation, with DC1 able to cross-present antigens to CD8+ T cells. Our study indicated that targeting GP96 on DCs may contribute to shaping T cell anti-tumor immunity.

Supported by grants from NIH NCI (R01:CA193939) and NIH NIAID (U01:AI125859)

Migratory type 2 dendritic cells mediate mucosal Th17 response to gut commensal bacteria

Dendritic cells (DCs) are professional antigen-presenting cells equipped with MHC-restricted antigens, co-stimulations, and cytokines that effectively prime and differentiate naïve T cells into distinct functional subsets. The immune signals that DCs carry reflect the route of antigen uptake and the innate stimuli they received. In the mucosal tissues, owing to the great variety of foreign antigens and inflammatory cues, DCs are predominantly activated and migratory. The gut commensal bacteria contribute to immune health by educating the immune system at this unique location interfacing with the outside environment. In the small intestine, CD4 Th17 cells are abundant and play a critical role in mucosal defense against bacterial and fungal infections. We identified that the early priming step of commensal-driven Th17 cells is controlled by bona fide Zbtb46-expressing DCs. CCR7-dependent migration of DC2s from the small intestine to the mesenteric lymph nodes is essential for the activation of naïve CD4 T cells. The migratory DC2 population in the MLN are almost exclusively Esam+ cells. Single-cell RNA sequencing highlighted the abundance of co-stimulatory markers (CD40 and OX40) and chemokines (Ccl22 and Cxcl16) on MLN migratory DCs. Further resolution of MLN migratory DC2s revealed that the Th17-polarizing cytokine IL-6 colocalizes with DC2s expressing CD40, Ccl17, and Ccl22. Our study indicates that the mucosal Th17 cell response is regulated by a restricted subset of migratory DC2s in the gut draining lymph nodes.

Supported by NIAID U01AI125859

Type-2 dendritic cells mediate control of cytotoxic T cell-resistant tumors

Type 2 DCs (DC2s) comprise the majority of conventional DCs within most tumors; however, little is known about their ability to initiate and sustain antitumor immunity, as most studies have focused on antigen cross-presenting DC1s. Here, we report that DC2 infiltration identified by analysis of multiple human cancer data sets showed a significant correlation with survival across multiple human cancers, with the benefit being seen in tumors resistant to cytotoxic T cell control. Characterization of DC subtype infiltration into an immunotherapy-resistant model of breast cancer revealed that impairment of DC1s through 2 unique models resulted in enhanced DC2 functionality and improved tumor control. BATF3 deficiency depleted intratumoral DC1s, which led to increased DC2 lymph node migration and CD4⁺ T cell activation. Enhancing DC2 stimulatory potential by genetic deletion of Hsp90b1 (encoding molecular chaperon GP96) led to a similar enhancement of T cell immunity and improved survival in a spontaneous breast cancer model. These data highlight the therapeutic and prognostic potential of DC2s within checkpoint blockade–resistant tumors.

Abstract 2649: An ex vivo 3D tumoroid model of fresh patient tissue (3D-EX) to assess the efficacy of anti-angiogenic compounds in renal cell carcinoma

Introduction: Renal Cell Carcinoma (RCC) is highly resistant to systemic chemotherapy; however, targeting pro-angiogenic pathways has shown significant clinical benefit. The development of targeted anti-angiogenetic agents has been hampered by the lack of clinically relevant models for screening. We have previously reported that the generation of 3D-tumoroids containing the unaltered tumor stroma could effectively be used to detect tumor response to small molecule inhibitors as well as antibody-based therapeutic agents. In this study we described a novel ex vivo platform to develop anti-angiogenic therapeutic strategies using fresh patient tumoroids of hepatocellular carcinoma and renal cell carcinoma.

Materials and Methods: All fresh tumor samples were obtained with patient consent and relevant IRB approval. For the ex vivo assays, 3D tumoroids measuring 150 µm in size were treated with tyrosine kinase inhibitors (TKIs) sunitinib, sorafenib or axitinib. Treatment-mediated changes in endothelial cell viability was assessed by the confocal-based high-content real time imaging platform using fluorescent labeled anti-CD31 and anti-VEGFR2 antibodies, combined with custom image analysis algorithms. Additionally, treatment-mediated changes in tumor immune cell composition including CD4 and CD8 T-cells, Tregs, NK cells, macrophages, cell surface expression of checkpoint proteins as well as T-cell activation were evaluated by multiplex flow cytometry.

Results: Our data shows that endothelial cells and capillary structures could clearly be visualized within3D tumoroids by confocal microscopy. Furthermore, we were able to quantify apoptotic cell death in endothelial cells induced by TKI inhibitors. Flow cytometry analysis demonstrated significant changes in T-cell activation upon treatment with TKIs that closely correlated with increased proinflammatory cytokine release. Observations found that the combination of anti-angiogenic treatments and immuno-modulatory agents significantly improved treatment responses.

Conclusion: The ex vivo platform described in this study allowed assessment of the effect of anti-angiogenetic TKIs on tumor capillary endothelial cells as well as on tumor resident immune cell populations in intact RCC tumoroids of fresh patient tumor samples. We believe this clinically relevant approach can be used to identify the most effective anti-angiogenic and immunotherapeutic drugs and drug combinations in RCC and may improve personalized therapy for individual patients in clinical studies.

Citation Format: Jared Ehrhart, Mibel M. Pabón, Stephen Iwanowycz, Zhisong Tong, Tina Pastoor, Soner Altiok. An ex vivo 3D tumoroid model of fresh patient tissue (3D-EX) to assess the efficacy of anti-angiogenic compounds in renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2649.

Abstract 1501: Employing 3D-ACT platform to assess the ability of stromal-targeting agents to improve penetration and efficacy of cell therapy

Background: Adoptive T cell therapy (ACT) has demonstrated great clinical success for the treatment of hematological malignancies. However, the unique challenges presented by solid tumors has significantly limited their utility. The primary characteristic of an effective ACT is the ability to selective identify tumor cells. In case of solid tumors, the ACT faces the additional hurdle requiring penetration into the tumor microenvironment (TME) while retaining function. Tumors develop highly immunosuppressive stroma which serves as a mechanical hinderance for the penetration and function of activated effector cells. In this study we used our 3D-ACT platform to investigate the ability of focal adhesion kinase (FAK) inhibitors to enhance the penetration of engineered cells into the intact patient tumor stroma and their efficacy within the tumor immune microenvironment.

Methods: All tumor samples were obtained with patient consent and relevant IRB approval. Unpropagated 3D tumoroids with intact TME measuring 150 µm in size were prepared from fresh tumor samples of renal cell carcinoma (RCC), and colorectal carcinoma (CRC) using proprietary technology developed at Nilogen Oncosystems. Engineered T cells were labeled with different cell tracker fluorescent dyes to monitor cell movements and locations within tumoroids by confocal analysis. 3D tumoroids were treated with vehicle only or FAK inhibitors and exposed to CAR-T cells at 10:1 E:T ratio. Cell penetration within tumoroids and tumor cell killing was measured by high-content confocal imaging combined with 3D-image analysis. ACT cell activation was monitored using multiparameter flow cytometry analysis and multiplex cytokine release assays to assess changes in the TME.

Results: Our studies demonstrated that the confocal-based high-content real time imaging platform, combined with custom image analysis algorithms, allowed for monitoring of treatment-mediated tumor cell killing with structural analysis of engineered T-cells in the intact 3D tumoroids. Our data revealed that CAR-T cell penetration into tumoroids greatly varied between different tumor types and was heavily influenced by the tumor's stromal components. Treatment with FAK-inhibitors led to alterations within the TME, which subsequently impacted penetration and efficacy of CAR-T cells as assessed by flow cytometry and confocal imaging.

Conclusion: The ex vivo model described here (3D-ACT) retains the TME and replicate the heterogeneity of tumor stroma to provide provides a clinically relevant platform to evaluate the influence of the tumor stromal components on engineered T cell functions. We believe the 3D-ACT platform can effectively be used to screen for drugs that can promote ACT penetration into the tumor stroma and survival within the tumor microenvironment.

Citation Format: Zhisong Tong, Stephen Iwanowycz, Jared Ehrhart, Mibel M. Pabón, Tina Pastoor, Soner Altiok. Employing 3D-ACT platform to assess the ability of stromal-targeting agents to improve penetration and efficacy of cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1501.

Molecular Chaperone GRP94/GP96 in Cancers: Oncogenesis and Therapeutic Target

During tumor development and progression, intrinsic and extrinsic factors trigger endoplasmic reticulum (ER) stress and the unfolded protein response, resulting in the increased expression of molecular chaperones to cope with the stress and maintain tumor cell survival. Heat shock protein (HSP) GRP94, also known as GP96, is an ER paralog of HSP90 and has been shown to promote survival signaling during tumor-induced stress and modulate the immune response through its multiple clients, including TLRs, integrins, LRP6, GARP, IGF, and HER2. Clinically, elevated expression of GRP94 correlates with an aggressive phenotype and poor clinical outcome in a variety of cancers. Thus, GRP94 is a potential molecular marker and therapeutic target in malignancies. In this review, we will undergo deep molecular profiling of GRP94 in tumor development and summarize the individual roles of GRP94 in common cancers, including breast cancer, colon cancer, lung cancer, liver cancer, multiple myeloma, and others. Finally, we will briefly review the therapeutic potential of selectively targeting GRP94 for the treatment of cancers.

Bone marrow deficiency of mRNA decaying protein Tristetraprolin increases inflammation and mitochondrial ROS but reduces hepatic lipoprotein production in LDLR knockout mice

Tristetraprolin (TTP), an mRNA binding and decaying protein, plays a significant role in controlling inflammation by decaying mRNAs encoding inflammatory cytokines such as TNFalpha. We aimed to test a hypothesis that TTP in bone marrow (BM) cells regulates atherogenesis by modulating inflammation and lipid metabolism through the modulation of oxidative stress pathways by TTP target genes. In a BM transplantation study, lethally irradiated atherogenic LDLR^-/- mice were reconstituted with BM cells from either wild type (TTP^+/+) or TTP knockout (TTP^-/-) mice, and fed a Western diet for 12 weeks. We made the following observations: (1) TTP^-/- BM recipients display a significantly higher systemic and multi-organ inflammation than TTP^+/+ BM recipients; (2) BM TTP deficiency modulates hepatic expression of genes, detected by microarray, involved in lipid metabolism, inflammatory responses, and oxidative stress; (3) TTP^-/- BM derived macrophages increase production of mitochondrial reactive oxygen species (mtROS); (4) BM-TTP^-/- mice display a significant reduction in serum VLDL/LDL levels, and attenuated hepatic steatosis compared to controls; and (5) Reduction of serum VLDL/LDL levels offsets the increased inflammation, resulting in no changes in atherosclerosis. These findings provide a novel mechanistic insight into the roles of TTP-mediated mRNA decay in bone marrow-derived cells in regulating systemic inflammation, oxidative stress, and liver VLDL/LDL biogenesis.

Specific Subset of Dendritic Cells Control the Priming of Mucosal Th17 Cells

Phagocytic mononuclear cells play an essential role in regulating gut immune homeostasis by sensing, internalizing microbial parts, and subsequently driving adaptive response in an antigen- and cytokine-dependent context. In a healthy host, physiological Th17 cells are predominantly generated in the gut, induced by local commensal microbiota. However, the precise subpopulation of antigen-presenting cells responsible for imprinting Th17 program in naïve CD4 T cells have not yet been definitively identified.

Objective

Mapping the functional subset of Th17-inducing dendritic cells (DCs) will uncover new targets for mucosal vaccine design.

Methods & Results

Using transgenic CD4 T cells specifically recognizing a gut-colonizing commensal bacterial antigen, we found that migratory DCs (CD11chiMHCIIhiZbtb46+) in the mesenteric lymph nodes are indispensable for the initial Th17 cell priming. Whereas the absence of CD103+ or CX3CR1+ DCs did not impact Th17 cell differentiation. Single cell RNA sequencing revealed that the migratory DCs are highly heterogeneous and consist of 8 clusters of transcriptionally specialized subsets. Interleukin-6, the Th17-polarizing cytokine, is expressed by a minor population of DCs with a type I interferon signature. Our results indicate that during homeostasis, Th17 cells activation in the mesenteric lymph nodes and later persistence in the small intestine may be controlled and sustained by different groups of antigen-presenting cells. The complexity and heterogeneity of mucosal DCs imply that other effector and regulatory T cell responses may be regulated by different DC subsets at this unique tissue environment.

Regulation of dendritic cell function improves survival in experimental sepsis through immune chaperone

Dendritic cells (DCs) are professional Ag-presenting cells that play a critical role in both innate and adaptive immune responses. DCs recognize and respond to bacteria through multiple PRRs, including TLRs. Heat shock protein gp96/grp94 is a master essential chaperone for TLRs in the endoplasmic reticulum. We generated DC-specific gp96-knockout (KO) mice and showed that gp96 KO DCs were unable to respond to multiple TLR ligands. TLR-mediated hyperinflammatory response can lead to sepsis. However, the roles of neither DCs nor the DC-intrinsic gp96 in the process are completely understood. In a LPS-induced sepsis model, we hereby found that deletion of gp96 in DCs significantly reduced serum TNF-α levels and improved survival. Furthermore, using the well-defined polymicrobial sepsis model of cecal ligation and puncture, we found that DC-specific ablation of gp96 improved survival with significantly attenuated liver and renal injuries, decreased circulating inflammatory cytokines, altered DC maturation and activation, and increased serum Ig. Collectively, we demonstrate that deletion of gp96 in DCs is beneficial in protecting mice against sepsis induced by both endotoxemia and polymicrobial infections. We conclude that targeting gp96 in DCs may provide a potential novel approach for reducing the morbidity and mortality of sepsis.

Anticancer activity of emodin is associated with downregulation of CD155

Emodin is a Chinese herb-derived compound that exhibits a variety of pharmacological benefits. Although emodin has been shown to inhibit growth of cancer cells, its antineoplastic function is incompletely understood. CD155 is a member of poliovirus receptor-related (PRR) family of adhesion molecules; it is constitutively expressed on many tumor cell lines and tissues and has diverse functions. CD155 has been reported to mediate activation of T cells via CD226 or inhibition of T cells via T-cell immunoreceptor with Ig and ITIM domains (TIGIT). In addition, CD155 may play a critical role through non-immunological mechanisms in cancer. In this study, we tested the ability of emodin to modulate CD155 expression in cancer cells. We found that emodin significantly decreased the expression of CD155 in tumor cells and inhibited tumor cell proliferation and migration, and induced cell-cycle arrest at G2/M phase. The tumor inhibitory effects of emodin were lost with CD155 knockdown. Furthermore, emodin was used to treat mice bearing B16 melanoma. It was shown that emodin attenuated tumor growth accompanied by suppressing CD155 expression. Therefore, we propose that emodin could inhibit tumor growth, and the antineoplastic properties of emodin are at least partially CD155 dependent. Our study provides new insights into the mechanisms by which emodin inhibits tumor growth.

Gut homeostasis and regulatory T cell induction depend on molecular chaperone gp96 in CD11c+ cells

The intestinal immunity and tolerance are orchestrated by both the innate and the adaptive immune system. Intestinal professional antigen presenting cells (pAPCs) recognize and respond to the gut microbiota through multiple pattern-recognition receptors, including TLRs and NLRs. How gut pAPCs maintain mucosal homeostasis remains incompletely understood. Heat shock protein gp96, also known as grp94, is an essential immune chaperone for TLRs. However, the role of gp96 in regulating CD11c⁺ APCs in the gut immunity and tolerance is unknown. By a genetic strategy, we report here that selective deletion of gp96 from CD11c⁺ cells in mice results in alteration of dendritic cell and T cell subsets in the gut as well as loss of antigen-specific regulatory T cell induction in the mesenteric lymph nodes. Strikingly, these conditional gp96-null mice developed spontaneous colitis, had increased levels of systemic and fecal IgA, and were highly susceptible to chemical-induced colitis. Our findings for the first time demonstrate that gp96 is essential for CD11c⁺ cells to induce regulatory T cells and maintain gut homeostasis, illustrating the importance of protein immune chaperone in safeguarding against immune pathology.

Dendritic cell-intrinsic TLR signaling regulates polymicrobial sepsis

Dendritic cells (DCs) are professional antigen-presenting cells that play a critical role in both innate and adaptive immune response. DCs recognize and respond to bacteria through multiple pattern-recognition receptors, including Toll-like receptors (TLRs). Heat shock protein gp96 is a master chaperone for TLRs in the endoplasmic reticulum and plays critical roles in innate immunity. Sepsis is a clinical syndrome caused by a severe immune response to infection. However, the role of DC-intrinsic TLRs in sepsis has not been studied. Using a unique DC-specific gp96 knockout (KO) mouse model, we observed that gp96-deficient DCs were unable to respond to both surface and intracellular TLR ligands. Our DC-specific gp96 deficient mice present a DC-specific pan TLR KO mouse model. We challenged WT and KO mice with a lethal dose of LPS, and we found that WT mice significantly produced more serum TNF-a than did KO mice. Consistent with the detrimental effect of this cytokine in sepsis, we found that the WT mice were more susceptible to LPS-induced sepsis than the KO mice. Furthermore, using a well-defined sepsis model of cecal ligation and puncture (CLP), we found that KO mice exhibited significant higher survival rates (33%) compared to littermate WT controls (5%, p<0.05). Collectively, our study demonstrates that DC-specific gp96 KO mice were able to mount effective responses against polymicrobial sepsis, underscoring the importance of DC-intrinsic TLR signaling in innate immunity and sepsis outcomes.

Molecular chaperone is required for gut tolerogenic dendritic cell development and function

The intestinal mucosa is continuously inundated with foreign antigens. Therefore, immune cells need to be tightly regulated to maintain tolerance against harmless dietary antigens and microbiota while responding to pathogens. Intestinal dendritic cells (DCs) play an integral role in regulating immunity and tolerance because of their unique position at the interface of innate and adaptive immunity. Multiple populations of intestinal DCs have been reported based on the expression of CD103, CD11b, and CX3CR1. However, the mechanism by which different DC subsets regulate intestinal homeostasis is still unclear. Heat shock protein gp96 is an essential chaperone for most TLRs, integrins, and other proteins important for DC functions. However, the role of DC-intrinsic gp96 in regulating gut tolerance has not been studied. By a genetic strategy, we discovered that selective deletion of gp96 from CD11c+ cells in mice results in alteration of DC and T cell subsets in the gut as well as the loss of antigen-specific regulatory T cell (Treg) induction. Strikingly DC-specific gp96 knockout mice develop spontaneous colitis by 24 weeks of age. Furthermore, differentiation of murine bone marrow-derived DCs revealed that gp96 depletion selectively decreased cell maturation in response to FLT3L compared to CSF2. Also, gp96 depletion reduced DC migration and cross-presentation. Taken together, our results demonstrated that gp96 depletion from CD11c+ cells selectively inhibits tolerogenic DCs in the gut leading to decreased Treg cells, which indicates that DC-intrinsic gp96 plays essential roles in maintaining gut tolerance.

Transcriptional factor EB regulates macrophage polarization in the tumor microenvironment

Tumor microenvironment (TME) contains a variety of infiltrating immune cells. Among them, tumor-associated macrophages (TAMs) and their alternative activation contribute greatly to the progression of tumors. The mechanisms governing macrophage polarization in the TME are unclear. Here, we show that in TAMs or macrophages under tumor-conditioned medium treatment, the expression of transcription factor EB (TFEB) is reduced and more of the TFEB protein is in an inactive cytosolic form. Transforming growth factor (TGF)-β is identified as a main driving force for the reduced TFEB expression and activity in TAMs via activating ERK signaling. TFEB interference in macrophages significantly enhanced their alternative activation, with reduced expression of MHC-II and co-stimulatory molecule CD80, decreased ability to activate T cells, and increased ability to attract tumor cells. When co-inoculated with tumor cells, macrophages with TFEB knockdown significantly enhanced tumor growth with increased infiltration of M2-like macrophages, reduced infiltration of CD8⁺ T cells, and enhanced angiogenesis in the tumors. Mechanistic studies revealed that TFEB downregulation resulted in macrophage M2 polarization through reducing SOCS3 production and enhancing STAT3 activation. We further demonstrate that the activation of TFEB by hydroxypropyl-β-cyclodextrin in macrophages suppressed their M2 polarization and tumor-promoting capacity, and that macrophage-specific TFEB overexpression inhibited breast tumor growth in mice. Therefore, our data suggest that TFEB plays critical roles in macrophage polarization, and the downregulation of TFEB expression and activation is an integral part of tumor-induced immune editing in the TME. This study provides a rationale for a new cancer treatment strategy by modulating macrophage polarization through activating TFEB.

microRNA-155 deficiency impairs dendritic cell function in breast cancer

In antitumor immunity, dendritic cells (DCs) capture, process, and present tumor antigens to T cells, initiating a tumoricidal response. However, DCs are often dysfunctional due to their exposure to the tumor microenvironment (TME), leading to tumor escape from immune surveillance. Here, a vital role of microRNA-155 (miR-155) in regulating the function of DCs in breast cancer is reported. Host miR-155 deficiency enhanced breast cancer growth in mice, accompanied by reduced DCs in the tumors and draining lymph nodes. miR-155 deficiency in DCs impaired their maturation, migration ability, cytokine production, and the ability to activate T cells. We demonstrate that miR-155 regulates DC migration through epigenetic modulation of CCR7 expression. Moreover, IL-6 and IL-10, two cytokines abundant in the TME, are found to impair DC maturation by suppressing miR-155 expression. Furthermore, animal studies show that a lack of miR-155 diminishes the effectiveness of DC-based immunotherapy for breast cancer. In conclusion, these findings suggest that miR-155 is a master regulator of DC function in breast cancer, including maturation, cytokine secretion, migration toward lymph nodes, and activation of T-cells. These results suggest that boosting the expression of a single microRNA, miR-155, may significantly improve the efficacy of DC-based immunotherapies for breast cancer.

Ursolic acid enhances macrophage autophagy and attenuates atherogenesis

Macrophage autophagy has been shown to be protective against atherosclerosis. We previously discovered that ursolic acid (UA) promoted cancer cell autophagy. In the present study, we aimed to examine whether UA enhances macrophage autophagy in the context of atherogenesis. Cell culture study showed that UA enhanced autophagy of macrophages by increasing the expression of Atg5 and Atg16l1, which led to altered macrophage function. UA reduced pro-interleukin (IL)-1β protein levels and mature IL-1β secretion in macrophages in response to lipopolysaccharide (LPS), without reducing IL-1β mRNA expression. Confocal microscopy showed that in LPS-treated macrophages, UA increased LC3 protein levels and LC3 appeared to colocalize with IL-1β. In cholesterol-loaded macrophages, UA increased cholesterol efflux to apoAI, although it did not alter mRNA or protein levels of ABCA1 and ABCG1. Electron microscopy showed that UA induced lipophagy in acetylated LDL-loaded macrophages, which may result in increased cholesterol ester hydrolysis in autophagolysosomes and presentation of free cholesterol to the cell membrane. In LDLR(-/-) mice fed a Western diet to induce atherogenesis, UA treatment significantly reduced atherosclerotic lesion size, accompanied by increased macrophage autophagy. In conclusion, the data suggest that UA promotes macrophage autophagy and, thereby, suppresses IL-1β secretion, promotes cholesterol efflux, and attenuates atherosclerosis in mice.

Emodin Inhibits Breast Cancer Growth by Blocking the Tumor-Promoting Feedforward Loop between Cancer Cells and Macrophages

Macrophage infiltration correlates with severity in many types of cancer. Tumor cells recruit macrophages and educate them to adopt an M2-like phenotype through the secretion of chemokines and growth factors, such as MCP1 and CSF1. Macrophages in turn promote tumor growth through supporting angiogenesis, suppressing antitumor immunity, modulating extracellular matrix remodeling, and promoting tumor cell migration. Thus, tumor cells and macrophages interact to create a feedforward loop supporting tumor growth and metastasis. In this study, we tested the ability of emodin, a Chinese herb-derived compound, to inhibit breast cancer growth in mice and examined the underlying mechanisms. Emodin was used to treat mice bearing EO771 or 4T1 breast tumors. It was shown that emodin attenuated tumor growth by inhibiting macrophage infiltration and M2-like polarization, accompanied by increased T-cell activation and reduced angiogenesis in tumors. The tumor inhibitory effects of emodin were lost in tumor-bearing mice with macrophage depletion. Emodin inhibited IRF4, STAT6, and C/EBPβ signaling and increased inhibitory histone H3 lysine 27 tri-methylation (H3K27m3) on the promoters of M2-related genes in tumor-associated macrophages. In addition, emodin inhibited tumor cell secretion of MCP1 and CSF1, as well as expression of surface anchoring molecule Thy-1, thus suppressing macrophage migration toward and adhesion to tumor cells. These results suggest that emodin acts on both breast cancer cells and macrophages and effectively blocks the tumor-promoting feedforward loop between the two cell types, thereby inhibiting breast cancer growth and metastasis. Mol Cancer Ther; 15(8); 1931-42. ©2016 AACR.

Emodin Bidirectionally Modulates Macrophage Polarization and Epigenetically Regulates Macrophage Memory

Macrophages are pleiotropic cells capable of performing a broad spectrum of functions. Macrophage phenotypes are classified along a continuum between the extremes of proinflammatory M1 macrophages and anti-inflammatory M2 macrophages. The seemingly opposing functions of M1 and M2 macrophages must be tightly regulated for an effective and proper response to foreign molecules or damaged tissue. Excessive activation of either M1 or M2 macrophages contributes to the pathology of many diseases. Emodin is a Chinese herb-derived compound and has shown potential to inhibit inflammation in various settings. In this study, we tested the ability of emodin to modulate the macrophage response to both M1 and M2 stimuli. Primary mouse macrophages were stimulated with LPS/IFNγ or IL4 with or without emodin, and the effects of emodin on gene transcription, cell signaling pathways, and histone modifications were examined by a variety of approaches, including microarray, quantitative real-time PCR, Western blotting, chromatin immunoprecipitation, and functional assays. We found that emodin bidirectionally tunes the induction of LPS/IFNγ- and IL4-responsive genes through inhibiting NFκB/IRF5/STAT1 signaling and IRF4/STAT6 signaling, respectively. Thereby, emodin modulates macrophage phagocytosis, migration, and NO production. Furthermore, emodin inhibited the removal of H3K27 trimethylation (H3K27m3) marks and the addition of H3K27 acetylation (H3K27ac) marks on genes required for M1 or M2 polarization of macrophages. In conclusion, our data suggest that emodin is uniquely able to suppress the excessive response of macrophages to both M1 and M2 stimuli and therefore has the potential to restore macrophage homeostasis in various pathologies.

Emodin inhibits breast cancer growth by modulating the phenotype of tumor-associated macrophages (TUM6P.1004)

Infiltration of macrophages into breast tumors is correlated with increased metastasis and decreased patient survival. Activated macrophages display a spectrum of phenotypes, at either end of which are pro-inflammatory/anti-tumor M1 or anti-inflammatory/pro-tumor M2 macrophages. Tumors recruit macrophages to the primary site as well as to pre-metastatic niches, educate them to adopt an M2-like phenotype, and thereby create an immunosuppressive microenvironment. We previously showed that Chinese herb derived compound emodin has the potential to inhibit tumor metastasis by targeting tumor cell-macrophage interactions. Here we tested the ability of emodin to inhibit breast cancer growth in mice and examined the underlying mechanisms. Emodin was used to treat mice bearing EO771 or 4T1 breast tumors. We found that emodin treatment reduced M2-like macrophages in the primary tumors and the lungs, blunted the growth of primary tumors, and attenuated lung metastasis. Further in vitro studies showed that emodin modulates macrophage polarization and function through affecting multiple intracellular signaling pathways as well as through possible regulation of the epigenetic landscape. These results suggest that emodin can be developed as an anti-breast cancer therapy by its virtue of modulating the phenotype of tumor-associated macrophages.

Emodin suppresses pulmonary metastasis of breast cancer accompanied with decreased macrophage recruitment and M2 polarization in the lungs

Breast cancer is the leading cause of death in female cancer patients due to the lack of effective treatment for metastasis. Macrophages are the most abundant immune cells in the primary and metastatic tumors, and contribute to tumor initiation, progression, and metastasis. Emodin has been found to exert anti-tumor effects through promoting cell cycle arrest and apoptosis, and inhibiting angiogenesis, but its effects on tumor-associated macrophages during cancer metastasis have not been investigated. Mice inoculated with 4T1 or EO771 breast cancer cells orthotopically were treated with Emodin after the primary tumors reached 200 mm3 in size. Primary tumor growth, lung metastasis, and macrophage infiltration in the lungs were analyzed. In vitro experiments were performed to examine the effects of Emodin on macrophage migration and M2 polarization, and the underlying mechanisms. Emodin significantly suppressed breast cancer lung metastasis in both orthotopic mouse models without apparent effects on primary tumors. Reduced infiltration of F4/80+ macrophages and Ym1+ M2 macrophages in lungs was observed in Emodin-treated mice. In vitro experiments demonstrated that Emodin decreased the migration of macrophages toward tumor cell-conditioned medium (TCM) and inhibited macrophage M2 polarization induced by TCM. Mechanistically, Emodin suppressed STAT6 phosphorylation and C/EBPβ expression, two crucial signaling events in macrophage M2 polarization, in macrophages treated with IL-4 or TCM. Taken together, our study, for the first time, demonstrated that Emodin suppressed pulmonary metastasis of breast cancer probably through inhibiting macrophage recruitment and M2 polarization in the lungs by reducing STAT6 phosphorylation and C/EBPβ expression.

MicroRNA-155 deficiency enhances the recruitment and functions of myeloid-derived suppressor cells in tumor microenvironment and promotes solid tumor growth

Immune cells in tumor microenvironment play a prominent role in tumor progression and metastasis. MicroRNA-155 (miR-155) represents an important player in innate and adaptive immunity by regulating differentiation, maturation and activation of macrophages, dendritic cells, B cells and T cells. However, the role of miR-155 expression in immune cells in solid tumor development is less elucidated. Our current study showed that both B16-F10 melanoma and Lewis lung carcinoma tumors grew much faster in bic/miR-155 knockout (miR-155(-/-) ) mice along with an increase of myeloid-derived suppressor cells (MDSCs) accumulation in tumors, compared to that in wild-type mice. Bone marrow transplantation study showed that bone marrow miR-155 deficiency could replicate the above tumor-promoting phenotype. In vitro study demonstrated that tumor-infiltrating miR-155(-/-) MDSCs showed greater migration ability and expressed higher level of multiple chemokines. Furthermore, we found that the level of HIF-1α, a direct target of miR-155, was increased in miR-155 deficient MDSCs, and that the increased HIF-1α upregulated CXCL1, CXCL3 and CXCL8 expression in MDSCs, contributing to the enhanced recruitment of miR-155(-/-) MDSCs to the tumors. Moreover, miR-155(-/-) MDSCs showed enhanced immunosuppressive and pro-angiogenic capacities. Taken together, our study, for the first time, demonstrated that miR-155 deficiency promoted solid tumor growth through increasing the recruitment of MDSCs to tumor microenvironment and enhancing the tumor-promoting functions of the recruited MDSCs. Thus, upregulating miR-155 expression in MDSCs may be developed as a therapeutic approach to halt tumor development.

Emodin attenuates systemic and liver inflammation in hyperlipidemic mice administrated with lipopolysaccharides

Non-alcoholic fatty liver disease (NAFLD) is a major epidemics of the modern societies and has an inflammatory component in the pathogenesis. However, approved anti-inflammatory therapies are not currently available for the prevention of the transition from simple steatosis to non-alcoholic steatohepatitis (NASH). We aimed to test if a Chinese herb-derived compound, emodin could halt the simple steatosis to NASH transition. LDLR^-/- mice were fed a western-type diet for 10 weeks; and during the last four weeks, the mice were intra-peritoneally injected daily with LPS with or without emodin. Systemic inflammation was evaluated by measurement of serum levels of cytokines and chemokines and flow cytometric analysis of spleen leukocytes. Liver inflammation was determined by histology, immunocytochemistry and flow cytometry. Quantitative real-time PCR and Western blot were performed to examine the effects of emodin on LPS-induced inflammatory responses in macrophages. Our data showed that emodin ameliorated systemic inflammation, reduced inflammatory cell infiltration in the liver, and attenuated liver function impairment. In vitro experiments showed emodin inhibited LPS-induced expression of proinflammatory cytokines in macrophages through suppressing Erk1/2 and p38 signaling. In conclusion, emodin inhibited the transition from simple steatosis to NASH in hyperlipidemic mice challenged with LPS through suppressing systemic and macrophage inflammation. Emodin may be developed as a therapy for NAFLD by the virtue of its anti-inflammatory effects.