Accumulation Of Tumor-associated Macrophages Research Articles

Egfl6 promotes ovarian cancer progression by enhancing the immunosuppressive functions of tumor-associated myeloid cells.

Tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) play a critical role in resistance to immunotherapy. In this study, we identified epidermal growth factor-like 6 (Egfl6) as a regulator of myeloid cell functions. Our analyses indicated that Egfl6, via binding with β3 integrins and activation of p38 and SYK signaling, acts as a chemotactic factor for myeloid cell migration and promotes their differentiation toward an immunosuppressive state. In syngeneic mouse models of ovarian cancer (OvCa), tumor expression of Egfl6 increased the intratumoral accumulation of polymorphonuclear (PMN) MDSCs and TAMs and their expression of immunosuppressive factors, including CXCL2, IL-10, and PD-L1. Consistent with this, in an immune 'hot' tumor model, Egfl6 expression eliminated response to anti-PD-L1 therapy, while Egfl6 neutralizing antibody decreased the accumulation of tumor-infiltrating CD206+ TAMs and PMN-MDSCs and restored the efficacy of anti-PD-L1 therapy. Supporting a role in human tumors, in human OvCa tissue samples, areas of high EGFL6 expression colocalized with myeloid cell infiltration. scRNA-Seq analyses revealed a correlation between EGFL6 and immune cell expression of immunosuppressive factors. Our data provide mechanistic insights into the oncoimmunologic functions of EGFL6 in mediating tumor immune suppression and identified EGFL6 as a potential therapeutic target to enhance immunotherapy in patients with OvCa.

The fatty acid receptor CD36 promotes macrophage infiltration via p110γ signaling to stimulate metastasis

IntroductionMetabolic regulators are key in controlling immune cell fate in the tumor microenvironment. The accumulation of tumor-associated macrophages (TAMs) in cancer greatly contributes to metastasis and poor outcome. However, the metabolic pathways responsible for TAM accumulation are largely unknown. ObjectiveThis study aims to elucidate the role of the fatty acid translocase CD36 in the regulation of TAM accumulation. MethodsThe immune profile was analyzed in patients with liver metastasis by CIBERSORT. Immunohistostaining of CD68 and CD36 was conducted in clinical specimens from patients with liver metastasis. Myeloid-specific CD36 knockout mice and their littermates were used to establish preclinical liver metastasis models. Subsequently, a series of experiments were used to explore the underlying mechanisms of how CD36 regulates TAM population. ResultsWe found that massive TAM accumulation in patients with liver metastasis is associated with an upregulation of CD36 on TAMs. Liver metastasis is abundantly infiltrated by TAMs that are derived from circulating monocytes, but not tissue-resident macrophages. Myeloid-specific CD36 knockout specifically reduced and inactivated monocyte-differentiated macrophages, resulting in diminished immune suppression and attenuated liver metastasis. The protect effects of CD36 knockout can be abrogated by blockade of macrophage recruitment through CCR2 or the p110γ isoform of PI3K downstream of it. Mechanically, CD36 reprogrammed the lipid metabolism of macrophages, in which sphingolipids were significantly downregulated, that contributed to weakened lipid raft-dependent activation of p110γ. ConclusionCD36 expands TAM population by promoting the recruitment of circulating monocytes through CCL2/CCR2/p110γ signaling. Our findings provide evidence for targeting CD36 as a therapeutic strategy against liver metastasis.

Endocannabinoid Receptor 2 Function is Associated with Tumor-Associated Macrophage Accumulation and Increases in T Cell Number to Initiate a Potent Antitumor Response in a Syngeneic Murine Model of Glioblastoma.

Introduction: Glioblastoma patients have a highly immunosuppressive tumor microenvironment and systemic immunosuppression that comprise a major barrier to immune checkpoint therapy. Based on the production of endocannabinoids by glioblastomas, we explored involvement of endocannabinoid receptor 2 (CB2R), encoded by the CNR2 gene, which is predominantly expressed by immune cells, in glioblastoma-related immunosuppression. Materials & Methods: Bioinformatics of human glioblastoma databases was used to correlate enzymes involved in the synthesis and degradation of endocannabinoids, as well as CB2Rs, with patient overall survival. Intrastriatal administration of luciferase-expressing, murine GL261 glioblastoma cells was used to establish in in vivo glioblastoma model for characterization of tumor growth and intratumoral immune cell infiltration, as well as provide immune cells for in vitro co-culture experiments. Involvement of CB2Rs was determined by treatment with CB2R agonist (GW405833) or CB2R antagonist (AM630). ELISA, FACS, and immunocytochemistry were used to determine perforin, granzyme B, and surface marker levels. Results: Bioinformatics of human glioblastoma databases showed high expression of CB2R and elevated endocannabinoid production correlated with poorer prognosis, and involved immune-associated pathways. AM630treatment of GL261 glioblastoma-bearing mice induced a potent antitumor response, with survival plateauing at 50% on Day 40, when all control mice (median survival 28 days) and mice treated with GW405833 (median survival 21 days) had died. Luciferase tumor imaging revealed accelerated tumor growth by GW405833 treatment, but stable or regressing tumors in AM630-treated mice. Notably, in spleens, AM630 treatment caused an 83% decrease in monocytes/macrophages, and 1.8- and 1.6-fold increases in CD8+ and CD4+ cells, respectively. Within tumors, there was a corresponding decrease in tumor-associated macrophages (TAMs) and increase in CD8+ T cells. In vitro, lymphocytes from AM630-treated mice showed greater cytotoxic function (increased percentage of perforin- and granzyme B-positive CD8+ T cells). Discussion: These results suggest that inhibition of CB2R enhances both immunosuppressive TAM infiltration and systemic T-cell suppression through CB2R activation, and that inhibition of CB2Rs can potently counter both the immunosuppressive tumor microenvironment, as well as systemic immunosuppression in glioblastoma.

Definitive chemoradiotherapy induces T-cell-inflamed tumor microenvironment in unresectable locally advanced esophageal squamous cell carcinoma.

Chemoradiotherapy (CRT) modulates the tumor immune microenvironment of multiple cancer types, including esophageal cancer, which potentially induces both immunogenicity and immunosuppression by upregulating the presentation of tumor-specific antigens and immune checkpoint molecules in tumors, respectively. The prognostic effects of immune modification by CRT in esophageal squamous cell carcinoma (ESCC) remain controversial because of the lack of detailed immunological analyses using paired clinical specimens before and after CRT. We aimed to clarify the immunological changes in the tumor microenvironment caused by CRT and elucidate the predictive importance of clinical response and prognosis and the rationale for the necessity of subsequent programmed cell death protein 1 (PD-1) inhibitor treatment. In this study, we performed a comprehensive immunological analysis of paired biopsy specimens using multiplex immunohistochemistry before and after CRT in patients with unresectable locally advanced ESCC. CRT significantly increased the intra-tumoral infiltration and PD-1 expression of CD8+ T cells and conventional CD4+ T cells but decreased those of regulatory T cells and the accumulation of tumor-associated macrophages. Multivariate analysis of tumor-infiltrating T-cell phenotypes revealed that the density of PD-1+CD8+ T cells in the tumor after CRT could predict a confirmed complete response and favorable survival. This study showed that CRT improved the immunological characteristics of unresectable locally advanced ESCC and identified the density of PD-1+CD8+ T cells as a predictive factor for prognosis. This finding supports the rationale for the necessity of subsequent PD-1 inhibitor treatment.

TGF-β1-Induced SOX18 Elevation Promotes Hepatocellular Carcinoma Progression and Metastasis Through Transcriptionally Upregulating PD-L1 and CXCL12

Background and aimsHepatocellular carcinoma (HCC) is characterized by an immune-suppressive microenvironment, which contributes to tumor progression, metastasis and immunotherapy resistance. Identification of HCC-intrinsic factors regulating immunosuppressive microenvironment is urgently needed. Here, we aimed to elucidate the role of SYR-Related High-Mobility Group Box 18 (SOX18) in inducing immunosuppression and to validate novel combination strategies for SOX18-mediated HCC progression and metastasis. MethodsThe role of SOX18 in HCC was investigated in orthotopic allografts and diethylinitrosamine/carbon tetrachloride (DEN/CCl4) induced spontaneous models by using murine cell lines, adeno-associated virus 8 and hepatocyte-specific knockin and knockout mice. The immune cellular composition in HCC microenvironment was evaluated by flow cytometry and immunofluorescence. ResultsSOX18 overexpression promoted the infiltration of tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) while diminishing cytotoxic T cells to facilitate HCC progression and metastasis in cell-derived allografts and chemically-induced HCC models. Mechanistically, transforming growth factor-beta 1 (TGF-β1) upregulated SOX18 expression by activating the Smad2/3 complex. SOX18 transactivated chemokine (C-X-C motif) ligand 12 and programmed death ligand 1 (PD-L1) to induce the immunosuppressive microenvironment. CXCL12 knockdown significantly attenuated SOX18-induced TAMs and Tregs accumulation and HCC dissemination. Antagonism of CXCR4, the cognate receptor of CXCL12, or selective knockout of CXCR4 in TAMs or Tregs likewise abolished SOX18-mediated effects. TGFβR1 inhibitor Vactosertib or CXCR4 inhibitor AMD3100 in combination with anti-PD-L1 dramatically inhibited SOX18-mediated HCC progression and metastasis. ConclusionsSOX18 promoted the accumulation of immunosuppressive TAMs and Tregs in microenvironment by transactivating CXCL12 and PD-L1. CXCR4 inhibitor or TGFβR1 inhibitor in synergy with anti-PD-L1 represented a promising combination strategy to suppress HCC progression and metastasis.

The Uridylyl Transferase TUT7-Mediated Accumulation of Exosomal miR-1246 Reprograms TAMs to Support CRC Progression.

Tumor-associated macrophages (TAMs) play a crucial role in promoting tumor growth and dissemination, motivating a search for key targets to interfere with the activation of TAMs or reprogram TAMs into the tumor-suppressive type. To gain insight into the mechanisms of macrophage polarization, a designed co-culture system is established, allowing for the education of macrophages in a manner that closely mimics the intricacies of TAMs in the tumor immune microenvironment (TIME). Through database mining, exosomal miR-1246 is identified and is then validated. Exosomal miR-1246-driven polarization of TAMs disrupts the infiltration and function of CD8+ T cells. Mechanically, the amassment of exosomal miR-1246 stems from TUT7-mediated degradation of small noncoding RNA, a process stabilized by SNRPB, but not the precursor of miR-1246. Moreover, an Exo-motif is present in the exosomal miR-1246 sequence, enabling it to bind with the exosomal sorting protein hnRNPA2B1. RNA-seq analysis reveals that exogenous miR-1246 modulates the polarization of TAMs at a post-transcriptional level, emphasizing the pivotal role of the NLRP3 in macrophage polarization. In conclusion, the findings underscore the importance of exosomal miR-1246 as a trigger of macrophage reprogramming and uncover a novel mechanism for its enhanced presence in the TIME.

STEM-05. HYPOXIA AND ACIDOSIS PROMOTE YAP/TAZ ACTIVATION, POTENTIALLY SUPPORTING GLIOMA STEM CELL MAINTENANCE IN THE PERI-NECROTIC ZONES

Abstract Glioblastoma (GBM) is a highly malignant brain tumor characterized by rapid growth and poor clinical outcomes. The development of necrosis is associated with massive tumor microenvironment (TME) reshaping and rapid progression characterized by accumulation of tumor-associated macrophages (TAMs) and glioma stem cells (GSCs) in peri-necrotic zones. Using Ivy-GAP and single-cell RNA seq data, we found that many canonical stem-cell associated transcription factors (SOX2, OLIG2, FOXM1) were not upregulated in the hypoxic peri-necrotic zone, yet Hippo transcriptional activation was consistently noted under these conditions. We hypothesized that Hippo activation promotes GSC stemness and may be due to direct effects of hypoxic; the acidic conditions associated with necrosis; or by cytokines secreted by adjacent TAMs. Using patient-derived GBM neurosphere cultures, we exposed glioma cells to 1% hypoxia and found that nuclear expression of YAP1 and TAZ, as well as Hippo pathway readout CYR61, were upregulated compared to normoxia (21%) at 48 hrs, indicating Hippo activation. Exposing cells to an acidic environment (pH 6.3) also caused Hippo transcriptional activation independent of hypoxia. Using single-cell RNA-seq data, we uncovered potential hypoxia-regulated upstream genes that could be responsible for nuclear YAP/TAZ transportation under hypoxia, including Zyxin, WBP2, and PP2A. We also found that culturing GBM cells with media conditioned by human primary macrophages activated Hippo transcription. Using human cytokine arrays, we identified cytokines that showed increased levels in TAM-conditioned media, including EGF, CXCL8, TGF-β, and CXCL5. Treating GBM cells with either hypoxia or a pharmacological activator of YAP/TAZ led to the upregulation of proteins in the inhibitor of differentiation (ID) family (ID1, ID2), which could represent a downstream mechanism related to stem-like behavior following Hippo activation. Our data support the conclusion that hypoxia and TAM cytokines directly stimulate YAP/TAZ activation to potentially promote GSC maintenance in the GBM peri-necrotic niche.

FAM171B stabilizes vimentin and enhances CCL2-mediated TAM infiltration to promote bladder cancer progression

BackgroundInvasion and metastasis are the main causes of unfavourable prognosis in patients diagnosed with bladder cancer. The efficacy of immunotherapy in bladder cancer remains suboptimal due to the presence of an immunosuppressive microenvironment. The novel protein family with sequence similarity 171B (FAM171B) has been identified, but its precise role and mechanism in bladder cancer remain unclear.MethodsIn this study, we conducted an analysis to investigate the associations between FAM171B expression and the prognosis and clinicopathological stage of bladder cancer. To this end, we utilized RNA sequencing data from the TCGA and GEO databases, as well as tumor tissue specimens obtained from our clinical centre. RNA sequencing analysis allowed us to examine the biological function of FAM171B at the transcriptional level in bladder cancer cells. Additionally, we used immunoprecipitation and mass spectrometry to identify the protein that interacts with FAM171B in bladder cancer cells. The effects of FAM171B on modulating tumor-associated macrophages (TAMs) and vimentin-mediated tumor progression, as well as the underlying mechanisms, were clarified by phalloidin staining, immunofluorescence staining, ELISA, RNA immunoprecipitation, flow cytometry and a bladder cancer graft model.ResultsFAM171B expression exhibits strong positive correlation with poor survival outcomes and advanced clinicopathological stages in patients with bladder cancer. FAM171B significantly promoted bladder cancer growth and metastasis, accompanied by TAM accumulation in the microenvironment, in vivo and in vitro. Through studies of the molecular mechanism, we found that FAM171B contributes to tumor progression by stabilizing vimentin in the cytoplasm. Additionally, our research revealed that FAM171B enhances the splicing of CCL2 mRNA by interacting with heterogeneous nuclear ribonucleoprotein U (HNRNPU), ultimately leading to increased recruitment and M2 polarization of TAMs.ConclusionsIn this study, we identified FAM171B as a potent factor that promotes the progression of bladder cancer. These findings establish a solid theoretical foundation for considering FAM171B as a potential diagnostic and therapeutic biomarker for bladder cancer.

Multi-dimensional single-cell characterization revealed suppressive immune microenvironment in AFP-positive hepatocellular carcinoma

Alpha-fetoprotein (AFP)-secreting hepatocellular carcinoma (HCC), which accounts for ~75% of HCCs, is more aggressive with a worse prognosis than those without AFP production. The mechanism through which the interaction between tumors and the microenvironment leads to distinct phenotypes is not yet clear. Therefore, our study aims to identify the characteristic features and potential treatment targets of AFP-negative HCC (ANHC) and AFP-positive HCC (APHC). We utilized single-cell RNA sequencing to analyze 6 ANHC, 6 APHC, and 4 adjacent normal tissues. Integrated multi-omics analysis together with survival analysis were also performed. Further validation was conducted via cytometry time-of-flight on 30 HCCs and multiplex immunohistochemistry on additional 59 HCCs. Our data showed that the genes related to antigen processing and interferon-γ response were abundant in tumor cells of APHC. Meanwhile, APHC was associated with multifaceted immune distortion, including exhaustion of diverse T cell subpopulations, and the accumulation of tumor-associated macrophages (TAMs). Notably, TAM-SPP1+ was highly enriched in APHC, as was its receptor CD44 on T cells and tumor cells. Targeting the Spp1-Cd44 axis restored T cell function in vitro and significantly reduced tumor burden when treated with either anti-Spp1 or anti-Cd44 antibody alone or in combination with anti-Pd-1 antibody in the mouse model. Furthermore, elevated IL6 and TGF-β1 signaling contributed to the enrichment of TAM-SPP1+ in APHC. In conclusion, this study uncovered a highly suppressive microenvironment in APHC and highlighted the role of TAM-SPP1+ in regulating the immune microenvironment, thereby revealing the SPP1-CD44 axis as a promising target for achieving a more favorable immune response in APHC treatment.

Chronic psychological stress promotes breast cancer pre-metastatic niche formation by mobilizing splenic MDSCs via TAM/CXCL1 signaling

BackgroundEmerging studies have identified chronic psychological stress as an independent risk factor influencing breast cancer growth and metastasis. However, the effects of chronic psychological stress on pre-metastatic niche (PMN) formation and the underlying immunological mechanisms remain largely unknown.MethodsThe effects and molecular mechanisms of chronic unpredictable mild stress (CUMS) on modulating tumor-associated macrophages (TAMs) and PMN formation were clarified by multiplex immunofluorescence technique, cytokine array, chromatin immunoprecipitation, the dual-luciferase reporter assay, and breast cancer xenografts. Transwell and CD8+ T cytotoxicity detection were used to analyze the mobilization and function of myeloid-derived suppressor cells (MDSCs). mCherry-labeled tracing strategy and bone marrow transplantation were applied to explore the crucial role of splenic CXCR2+/+ MDSCs facilitating PMN formation under CUMS.ResultsCUMS significantly promoted breast cancer growth and metastasis, accompanied by TAMs accumulation in the microenvironment. CXCL1 was identified as a crucial chemokine in TAMs facilitating PMN formation in a glucocorticoid receptor (GR)-dependent manner. Interestingly, the spleen index was significantly reduced under CUMS, and splenic MDSCs were validated as a key factor mediating CXCL1-induced PMN formation. The molecular mechanism study revealed that TAM-derived CXCL1 enhanced the proliferation, migration, and anti-CD8+ T cell functions of MDSCs via CXCR2. Moreover, CXCR2 knockout and CXCR2−/−MDSCs transplantation significantly impaired CUMS-mediated MDSC elevation, PMN formation, and breast cancer metastasis.ConclusionOur findings shed new light on the association between chronic psychological stress and splenic MDSC mobilization, and suggest that stress-related glucocorticoid elevation can enhance TAM/CXCL1 signaling and subsequently recruit splenic MDSCs to promote PMN formation via CXCR2.Graphical

NLRP3 in tumor-associated macrophages predicts a poor prognosis and promotes tumor growth in head and neck squamous cell carcinoma.

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays cell- and tissue-specific roles in cancer, meaning that its activation in different tumors or cells may play different roles in tumor progression. We have previously described the tumor-promoting function of tumor-intrinsic NLRP3/IL-1β signaling in head and neck squamous cell carcinoma (HNSCC), but its role in immune cells remains unclear. In this study, we found that NLRP3 was highly expressed in tumor-associated macrophages (TAMs) in both mouse and human HNSCC, and the expression of NLRP3 was positively correlated with the density of TAMs according to immunohistochemistry, immunofluorescence, and flow cytometry analyses. Importantly, the number of NLRP3high TAMs was related to worse overall survival in HNSCC patients. Knocking out NLRP3 inhibited M2-like macrophage differentiation in vitro. Moreover, the carcinogenic effect induced by 4-nitroquinoline-1-oxide was decreased in Nlrp3-deficient mice, which had smaller tumor sizes. Genetic depletion of NLRP3 reduced the expression of protumoral cytokines, such as IL-1β, IL-6, IL-10, and CCL2, and suppressed the accumulation of TAMs and myeloid-derived suppressor cells (MDSCs) in mouse HNSCC. Thus, activation of NLRP3 in TAMs may contribute to tumor progression and have prognostic significance in HNSCC.

The Role of TAMs in Tumor Microenvironment and New Research Progress.

Tumor-associated macrophages (TAMs) are an important part of tumor microenvironment (TME) and play a key role in TME, participating in the process of tumor occurrence, growth, invasion, and metastasis. Among them, metastasis to tumor tissue is the key step of malignant development of tumor. In this paper, the latest progress in the role of TAMs in the formation of tumor microenvironment is summarized. It is particularly noteworthy that cell and animal experiments show that TAMs can provide a favorable microenvironment for the occurrence and development of tumors. At the same time, clinical pathological experiments show that the accumulation of TAMs in tumor is related to poor clinical efficacy. Finally, this paper discusses the feasibility of TAMs-targeted therapy as a new indirect cancer therapy. This paper provides a theoretical basis for finding a potentially effective macrophage-targeted tumor therapy.

Abstract 3146: EGFL6 induces immunosuppressive functions of tumor-associated myeloid cells and mediates resistance to anti-PDL1 therapy

Abstract Myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) are critical negative regulators of immunity in cancer. Understanding factors which regulate these cells could result in the identification of new approaches to enhance anti-tumor immunotherapy. One such factor is Epidermal growth factor-like 6 (EGFL6). EGFL6 is a secreted factor known to promote cancer stem like cell migration and regulate cancer cell differentiation. Similarly, EGFL6 promotes endothelial cell migration and proliferation. Indicating a potential role for EGFL6 as a myeloid cell regulatory factor, we found that mice which overexpress Egfl6 have an increased numbers of granulocytes and monocytes in both the bone marrow and spleen. In vitro and ex-vivo analysis indicated that EGFL6, via binding with beta integrins and activation of Syk/ERK signaling, (i) acts as a chemotactic factor for human myeloid cells migration and (ii) promotes their differentiation toward a suppressive state. Suggesting an important role in promoting an immunosuppressive tumor microenvironment (TME), using two syngeneic mouse models of ovarian cancer, we found that expression of Egfl6 in tumor cells resulted in increased accumulation of intra-tumoral MDSCs and TAMs and fewer cytotoxic CD8+ T cells. This was associated with increased tumor growth and shortened animal survival. Gene expression profiling and flow cytometry analysis of tumor infiltrating myeloid cells indicated that Egfl6 induced the expression of immunosuppressive factors, including CXCL2, IL-10 and PD-L1. Consistent with Egfl6 driving an immune suppressive TME, EGFL6 expression in an otherwise immune ‘hot’/anti-PD-L1 responsive tumor model completely inhibited response to anti-PD-L-1 therapy. We are currently evaluating the impact of Egfl6 neutralizing antibody on the efficacy of ICI therapy and anti-tumor immunity. Combined our data show that EGFL6 acts as a chemotactic factor to both recruit myeloid cells to the ovarian TME and subsequently promotes their differentiation to an immunosuppressive phenotype. This suggests EGFL6 is a potential novel therapeutic target to ovarian tumor mediated immunosuppression and enhance response to immune therapy in ovarian cancer patients. Citation Format: Sarah Sinno, Shoumei Bai, Claudia Coronnello, Anda Vlad, Ronald J. Buckanovich, Sandra Cascio. EGFL6 induces immunosuppressive functions of tumor-associated myeloid cells and mediates resistance to anti-PDL1 therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3146.

Exploring the Impact of TREM2 in Tumor-Associated Macrophages.

Simple SummaryTREM2+ macrophages were recently reported to be highly enriched and associated with immunosuppression in various cancer types. Hence, TREM2 targeting represents a new promising approach for cancer treatment that is based on reprogramming of tumor-associated macrophages to reshape anti-tumor immunity and overcome resistance to current therapies.Tumor-associated macrophages (TAMs) represent a key component of the tumor microenvironment and are generally associated with immunosuppression and poor prognosis. TREM2 is a transmembrane receptor of the immunoglobulin superfamily expressed in myeloid cells. TREM2 has been extensively studied in microglia and neurodegenerative diseases and recently emerged as a marker of pro-tumorigenic macrophages. The accumulation of TREM2-expressing TAMs was reported across numerous cancer patients and tumor models. TREM2 genetic blockade or TREM2 targeting with antibodies resulted in improved tumor control, enhanced response to anti-PD1, and significant changes in the tumor immune landscape. Preclinical studies paved the way for an ongoing clinical trial with a TREM2 depleting antibody and inspired further exploration of TREM2 targeting therapies. Here, we review the current knowledge about the impact of TREM2 in cancer, with an emphasis on the TREM2+ macrophage signature across different cancer types, the contribution of TREM2 to TAM phenotype and function, and the promising effects of TREM2 modulation.

Egfl6 promotes ovarian cancer progression by inducing the immunosuppressive functions of tumor-infiltrating myeloid cells.

Abstract Myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) are critical negative regulators of immunity in cancer. Understanding factors which regulate these cells could result in the identification of new approaches to enhance anti-tumor immunotherapy. One such factor is epidermal growth factor-like 6 (EGFL6), a secreted factor known to promote cancer stem like cell migration and regulate cancer cell differentiation. We found that mice which overexpress Egfl6 have an increased numbers of granulocytes and monocytes in both the bone marrow and spleen. In vitro and ex-vivo analysis indicated that EGFL6, via binding with beta integrins and activation of SYK and ERK signaling, (i) acts as a chemotactic factor for myeloid cells migration and (ii) promotes their differentiation toward a suppressive state. Suggesting an important role in promoting an immunosuppressive tumor microenvironment (TME), using two syngeneic mouse models of ovarian cancer, we found that expression of Egfl6 in tumor cells resulted in increased accumulation of intra-tumoral MDSCs and TAMs and fewer cytotoxic CD8+ T cells. This was associated with increased tumor growth and shortened animal survival. Gene expression profiling of tumor infiltrating myeloid cells indicated that Egfl6 induced the expression of immunosuppressive factors, including CXCL2, IL-10 and PD-L1. Moreover, in an immune ‘hot’ tumor model, EGFL6 completely inhibited response to a-PD-L-1 therapy. Combined our data show that EGFL6 induces the recruitment of myeloid cells into the ovarian TME and subsequently promotes their immunosuppressive functions. This suggest EGFL6 is a potential novel therapeutic target to enhance response to immune therapy in OvCa patients. Supported by Ovarian Cancer Research Alliance

Oncogenic Vav1-Myo1f induces therapeutically targetable macrophage-rich tumor microenvironment in peripheral Tcell lymphoma.

SUMMARYPeripheral T cell lymphoma not otherwise specified (PTCL-NOS) comprises heterogeneous lymphoid malignancies characterized by pleomorphic lymphocytes and variable inflammatory cell-rich tumor microenvironment. Genetic drivers in PTCL-NOS include genomic alterations affecting the VAV1 oncogene; however, their specific role and mechanisms in PTCL-NOS remain incompletely understood. Here we show that expression of Vav1-Myo1f, a recurrent PTCL-associated VAV1 fusion, induces oncogenic transformation of CD4+ T cells. Notably, mouse Vav1-Myo1f lymphomas show T helper type 2 features analogous to high-risk GATA3+ human PTCL. Single-cell transcriptome analysis reveals that Vav1-Myo1f alters T cell differentiation and leads to accumulation of tumor-associated macrophages (TAMs) in the tumor microenvironment, a feature linked with aggressiveness in human PTCL. Importantly, therapeutic targeting of TAMs induces strong anti-lymphoma effects, highlighting the lymphoma cells’ dependency on the microenvironment. These results demonstrate an oncogenic role for Vav1-Myo1f in the pathogenesis of PTCL, involving deregulation in T cell polarization, and identify the lymphoma-associated macrophage-tumor microenvironment as a therapeutic target in PTCL.

Immunostimulation of tumor microenvironment by targeting tumor-associated macrophages with hypoxia-responsive nanocomplex for enhanced anti-tumor therapy

Tumor-associated macrophages (TAMs), which dampen the therapeutic efficacy of cancer immunotherapy, are the key players in the immunosuppressive tumor microenvironment (TME). Therefore, reprogramming TAMs into tumoricidal M1 macrophages possesses considerable potential as a novel immunotherapy. However, the low bioavailability of polarization agents and limited accumulation of TAMs restrict their anti-tumor efficacy. In this study, we developed a polymer-based hypoxia-responsive nanocomplex to target TAMs in hypoxia for enhanced cancer immunotherapy. We synthesized a hypoxia-cleavable polymer poly(ethylene glycol)-azo-poly(l-lysine) (PEG-azo-PLL) and formulated a nanocomplex by simple mixing PEG-azo-PLL and poly(I:C). By mimicking in vitro hypoxia conditions, PEG-azo-PLL/poly(I:C) complexes could transform the physicochemical properties to enhance the delivery efficiency of poly(I:C) to tumor hypoxia, where M2-like TAMs are accumulated. Furthermore, PEG-azo-PLL/poly(I:C) could successfully reduce the population of M2-like TAMs in hypoxic tumors and promoted infiltration of CD8+ T cells in vivo, resulting in the favorable conversion of immunosuppressive TME. Finally, PEG-azo-PLL/poly(I:C) could elicit a significant in vivo anti-tumor effect in B16F10-bearing mice in addition to a prolonged survival time, demonstrating that the hypoxia-responsive nanocomplex PEG-azo-PLL/poly(I:C) is a promising approach for TAM reprogramming immunotherapy for solid tumors.

Abstract P012: Investigation of interleukin-34 dependent regulation of renal carcinoma tumor microenvironment

Abstract In 2020, Renal Carcinoma (RC) accounted for around 179,000 worldwide deaths and its mortality is predicted to double in the next 20 years. The major issue for RC patients is the absence of an efficient therapeutic option, especially for metastatic forms of the disease where the 5-years survival rate is close to 10%. The therapy of RC mainly targets the angiogenic and immunosuppressive tumor microenvironment (TME), but it is rarely curative and drug resistance is almost inevitable. Lack of validated biomarkers and scarce knowledge of the biological processes occurring during RC progression are main reasons of therapy failure. In our unpublished work, using a syngeneic murine model of RC, we identified interleukin-34 (IL34) as potential biomarker of RC progression. In particular, we observed that increased IL34 expression was associated with enhanced cancer cell aggressiveness and reduced survival both in mice and in RC patients from two different cohorts (i.e. KIRC-TCGA, and UroCCR local cohort). IL34 exerts pleiotropic functions in different biological processes, including immunity regulation, cell proliferation and monocytes survival and differentiation into macrophages. The expression of IL34 in the TME is heterogeneous between cancer types, and high IL34 levels can represent either a poor (i.e. in brain and lung cancers) or a favorable (i.e. in neck and breast cancers) prognostic factor. Regarding to RC, IL34 role in the TME still remains elusive and has never been described. For this reason, using the KIRC-TCGA database, we performed Gene Ontology enrichment analysis using a list of IL34 co-expressed genes to predict potential IL34 regulatory functions in the TME of RC patients. This analysis revealed that such genes are involved in different immune system related processes, including positive regulation of leukocyte activation, IL-10 production and adaptive immune response. Subsequently, using IL34-overexpressing murine renal carcinoma RENCA cells implanted in BALB/c mice, we investigated the IL34-dependent alteration of the tumor immune microenvironment. In particular, we observed that, both in generated primary tumors and lung metastases, IL34 increased the density of tumor associated macrophages (TAM), which expressed M2-type markers (e.g. Cd206 and Cd163). Furthermore, in these samples, qPCR analysis showed an increase of interleukin-10 gene expression suggesting that IL34 could induce an immunosuppressive microenvironment. Conversely, when we blocked IL34 activity in lung metastases using an inhibitor of CSF1R, the main receptor of IL34, we observed a significant reduction in TAM accumulation and Il10 expression. The major aim of this project is to investigate whether IL34 can sustain immunosuppression and, consequently, chemoresistance by accumulating TAM in the TME. Furthermore, the IL34-dependent regulation of other immune cell populations (e.g. T-reg or myeloid-derived suppressor cells) is under investigation. The study of IL34 role in the TME of RC can be fundamental to improve the current therapy. Citation Format: Andrea Emanuelli, Wilfried Souleyreau, Lindsay Cooley, Tiffanie Chouleur, Marie-Alix Derieppe, Jean-Christophe Bernhard, Andreas Bikfalvi. Investigation of interleukin-34 dependent regulation of renal carcinoma tumor microenvironment [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P012.

SIRT1 induces the accumulation of TAMs at colorectal cancer tumor sites via the CXCR4/CXCL12 axis

Our previous work suggested that high SIRT1 expression by cancer cells predicted a poor colorectal cancer (CRC) prognosis, but its role in the tumor microenvironment was unclear.Here, we examined tumor-infiltrating lymphocytes (TILs) in CRC expressing different levels of SIRT1. We also established a co-culture system with monocytes, CD8+ T cells and patient-derived tumor organoids (PDOs) to study the relationships between immune cells and cancer cells. The percentage of CD8+ T cells was decreased and the percentage of macrophages was increased in SIRT1-high (SIRT1-hi) CRC. Co-culture results showed that tumor-associated macrophages (TAMs) from SIRT1-hi CRC inhibited the proliferation and anti-tumor activity of CD8+ T cells. Importantly, SIRT1-hi CRC were shown to modulate the migration and the activity of TAMs. RNA sequencing revealed that CD14+ monocytes in SIRT1-hi patients expressed higher levels of CXCR4. Mechanistically, SIRT1 expression was shown to promote CXCL12 expression by inhibiting the acetylation of p53. Our findings indicate that SIRT1 in CRC induces TAM migration through the CXCR4/CXCL12 pathway, and inhibits the proliferation and activity of CD8+ T cells, resulting in promotion of CRC progression.

Comment on "Tumor-initiating cells establish an IL-33-TGF-β niche signaling loop to promote cancer progression".

Taniguchi et al (Research Articles, 17 July 2020, p. 269) claim that the cytokine interleukin-33 induces accumulation of tumor-associated macrophages expressing the immunoglobulin E receptor FcεRI. Although these findings hold great therapeutic promise, we provide evidence that the anti-FcεRI antibody used in this study is not specific for FcεRI on macrophages, which raises concerns about the validity of some of the conclusions.