Glioma Tumor-associated Macrophages Research Articles

Knockdown of trem2 promotes proinflammatory microglia and inhibits glioma progression via the JAK2/STAT3 and NF-κB pathways

BackgroundIn the tumor immune microenvironment (TIME), triggering receptor expressed on myeloid cells 2 (trem2) is widely considered to be a crucial molecule on tumor-associated macrophages(TAMs). Multiple studies have shown that trem2 may function as an immune checkpoint in various malignant tumors, mediating tumor immune evasion. However, its specific molecular mechanisms, especially in glioma, remain elusive.MethodsLentivirus was transfected to establish cells with stable knockdown of trem2. A Transwell system was used for segregated coculture of glioma cells and microglia. Western blotting, quantitative real-time polymerase chain reaction (qRT‒PCR), and immunofluorescence (IF) were used to measure the expression levels of target proteins. The proliferation, invasion, and migration of cells were detected by colony formation, cell counting kit-8 (CCK8), 5-ethynyl-2’-deoxyuridine (EdU) and transwell assays. The cell cycle, apoptosis rate and reactive oxygen species (ROS) level of cells were assessed using flow cytometry assays. The comet assay and tube formation assay were used to detect DNA damage in glioma cells and angiogenesis activity, respectively. Gl261 cell lines and C57BL/6 mice were used to construct the glioma orthotopic transplantation tumor model.ResultsTrem2 was highly overexpressed in glioma TAMs. Knocking down trem2 in microglia suppressed the growth and angiogenesis activity of glioma cells in vivo and in vitro. Mechanistically, knockdown of trem2 in microglia promoted proinflammatory microglia and inhibited anti-inflammatory microglia by activating jak2/stat1 and inhibiting the NF-κB p50 signaling pathway. The proinflammatory microglia produced high concentrations of nitric oxide (NO) and high levels of the proinflammatory cytokines TNF-α, IL-6, and IL-1β, and caused further DNA damage and promoted the apoptosis rate of tumor cells.ConclusionsOur findings revealed that trem2 in microglia plays a significant role in the TIME of gliomas. Knockdown of trem2 in microglia might help to improve the efficiency of inhibiting glioma growth and delaying tumor progression and provide new ideas for further treatment of glioma.

GPR65 sensing tumor-derived lactate induces HMGB1 release from TAM via the cAMP/PKA/CREB pathway to promote glioma progression

BackgroundLactate has emerged as a critical regulator within the tumor microenvironment, including glioma. However, the precise mechanisms underlying how lactate influences the communication between tumor cells and tumor-associated macrophages (TAMs), the most abundant immune cells in glioma, remain poorly understood. This study aims to elucidate the impact of tumor-derived lactate on TAMs and investigate the regulatory pathways governing TAM-mediated tumor-promotion in glioma.MethodsBioinformatic analysis was conducted using datasets from TCGA and CGGA. Single-cell RNA-seq datasets were analyzed by using UCSC Cell Browser and Single Cell Portal. Cell proliferation and mobility were evaluated through CCK8, colony formation, wound healing, and transwell assays. Western blot and immunofluorescence staining were applied to assess protein expression and cell distribution. RT-PCR and ELISA were employed to identify the potential secretory factors. Mechanistic pathways were explored by western blotting, ELISA, shRNA knockdown, and specific inhibitors and activators. The effects of pathway blockades were further assessed using subcutaneous and intracranial xenograft tumor models in vivo.ResultsElevated expressions of LDHA and MCT1 were observed in glioma and exhibited a positive correlation with M2-type TAM infiltration. Lactate derived from glioma cells induced TAMs towards M2-subtype polarization, subsequently promoting glioma cells proliferation, migration, invasion, and mesenchymal transition. GPR65, highly expressed on TAMs, sensed lactate-stimulation in the TME, fueling glioma cells malignant progression through the secretion of HMGB1. GPR65 on TAMs triggered HMGB1 release in response to lactate stimulation via the cAMP/PKA/CREB signaling pathway. Disrupting this feedback loop by GPR65-knockdown or HMGB1 inhibition mitigated glioma progression in vivo.ConclusionThese findings unveil the intricate interplay between TAMs and tumor cells mediated by lactate and HMGB1, driving tumor progression in glioma. GPR65, selectively highly expressed on TAMs in glioma, sensed lactate stimulation and fostered HMGB1 secretion via the cAMP/PKA/CREB signaling pathway. Blocking this feedback loop presents a promising therapeutic strategy for GBM.

Aggrephagy-related gene signature correlates with survival and tumor-associated macrophages in glioma: Insights from single-cell and bulk RNA sequencing.

Aggrephagy is a lysosome-dependent process that degrades misfolded protein condensates to maintain cancer cell homeostasis. Despite its importance in cellular protein quality control, the role of aggrephagy in glioma remains poorly understood. To investigate the expression of aggrephagy-related genes (ARGs) in glioma and in different cell types of gliomas and to develop an ARGs-based prognostic signature to predict the prognosis, tumor microenvironment, and immunotherapy response of gliomas. ARGs were identified by searching the Reactome database. We developed the ARGs-based prognostic signature (ARPS) using data from the Cancer Genome Atlas (TCGA, n = 669) by Lasso-Cox regression. We validated the robustness of the signature in clinical subgroups and CGGA cohorts (n = 970). Gene set enrichment analysis (GSEA) was used to identify the pathways enriched in ARPS subgroups. The correlations between ARGs and macrophages were also investigated at single cell level. A total of 44 ARGs showed heterogeneous expression among different cell types of gliomas. Five ARGs (HSF1, DYNC1H1, DYNLL2, TUBB6, TUBA1C) were identified to develop ARPS, an independent prognostic factor. GSEA showed gene sets of patients with high-ARPS were mostly enriched in cell cycle, DNA replication, and immune-related pathways. High-ARPS subgroup had higher immune cell infiltration states, particularly macrophages, Treg cells, and neutrophils. APRS had positive association with tumor mutation burden (TMB) and immunotherapy response predictors. At the single cell level, we found ARGs correlated with macrophage development and identified ARGs-mediated macrophage subtypes with distinct communication characteristics with tumor cells. VIM+ macrophages were identified as pro-inflammatory and had higher interactions with malignant cells. We identified a novel signature based on ARGs for predicting glioma prognosis, tumor microenvironment, and immunotherapy response. We highlight the ARGs-mediated macrophages in glioma exhibit classical features.

A Sampling of Highlights from the Literature.

Macrophages can be reprogrammed to promote antitumor responses (by Noah Smith via Wikimedia Commons).Multiple factors contribute to the suppression that occurs in the tumor microenvironment (TME) and this could potentially be alleviated through various mechanisms. Chen et al. find that high potassium in the TME inhibits antitumor responses from tumor-associated macrophages (TAM) via alteration of their metabolism. Blocking this metabolic switch enables TAMs to mount effective antitumor responses. Chryplewicz et al. find that TAMs in glioma are reprogrammed to a proinflammatory phenotype, along with other antitumor remodeling of the TME and tumor vasculature, after treatment with VEGF inhibitors and imipramine (tricyclic anti-depressant). These studies provide insight into multiple mechanisms of TAM suppression and potential targets that can be used to boost antitumor responses.Chen S, …, Wang D. Cell Metab 2022 September 13. DOI:10.1016/j.cmet.2022.08.016.Chryplewicz A, …, Hanahan D. Cancer Cell 2022 September 15;40:1111–27.E9.Dietary intake can affect microbiota and immunity (by the NCI via Wikimedia Commons).Dietary intake can affect antitumor immunity and response to immunotherapy. In a prospective study, Simpson et al. evaluated dietary patterns and microbial signatures of different patient populations and how these factors related to response to neoadjuvant immune checkpoint inhibition. Distinct differences between response groups were observed not only in microbial composition but also in immune-related adverse events. Specific diets, as well as certain microbial compositions, were associated with better treatment outcomes. The data highlight the crossroads of cancer-intrinsic and -extrinsic factors with patient lifestyle, and how these factors together can shape responses to treatment.Simpson RC, …, Long GV. Nat Med 2022 September 12. DOI:10.1038/s41591-022-01965-2.Immunotherapy can overcome resistance to HER2-targeted therapy (from IrinaPav via Wikimedia Commons).HER2-specific antibodies such as trastuzumab are used to treat HER2+ breast cancer, but not all patients respond and some that do ultimately relapse. Using orthogonal approaches, including analysis of tumor tissue and transcriptomic data from trastuzumab-treated patients with HER2+ breast cancer and a fully humanized immunocompetent model of HER2+ breast cancer, Rivas et al. find that a population of TGFβ-activated cancer-associated fibroblasts (CAF) and low IL2 activity associate with trastuzumab resistance. Targeting IL2 to fibroblast activation protein-α (FAP)–expressing cells restores tumor responsiveness to trastuzumab by enhancing NK cell–mediated antibody-dependent cytotoxicity, highlighting the therapeutic potential of targeting stromal components in the tumor microenvironment.Rivas EI, …, Calon A. Nat Commun 2022 September 9;13:5310.A Treg subpopulation of CAR T cells drives therapeutic resistance (from NIH via Flickr).Using single-cell profiling methods, two groups have identified subpopulations of CD19-targeting CAR T cells with T regulatory (Treg)–cell phenotypes associated with poor response in patients with B-cell lymphoma. Good et al. find a higher proportion of circulating CD4+Helios– Treg CAR T cells in patients with progressive disease who received axicabtagene ciloleucel (axi-cel), highlighting their potential as a biomarker prognostic for progression at day 7 post infusion. Haradhvala et al. similarly identify CAR+ Treg cells in blood and infusion products for patients nonresponsive to either axi-cel or tisagenlecleucel, and validate their role in mouse models of CAR T-cell treatment. The studies provide new insight into therapeutic resistance to CAR T-cell therapy.Good Z, …, Mackall CL. Nat Med 2022 September 12;28:1860–71.Haradhvala NJ, …, Maus MV. Nat Med 2022 September 12;28:1848–59.Covalent K-Ras(G12C) inhibitor provides a new target for immunotherapy (from Rawpixel).MHC class I presentation of tumor-specific peptides derived from intracellular proteins provides a target for anticancer therapy. Zhang et al. have identified a new class of therapeutically targetable MHC class I epitopes: covalently modified intracellular proteins. K-Ras(G12C) covalently conjugated to the K-Ras(G12C)-specific inhibitor ARS1620 can undergo antigen processing and presentation on MHC class I. ARS1620-specific antibodies can recognize MHC class I–restricted ARS1620-peptides. Incorporating such an antibody into a bispecific T-cell engager (BiTE) induces T-cell responses against K-Ras(G12C) tumor cells, suggesting a new strategy for cancer immunotherapy.Zhang Z, …, Craik CS. Cancer Cell 2022 September 12;40:1060–69.e7.NK cells are key component of the antitumor immune response (from NIAID via Wikimedia Commons).Understanding the factors that regulate the maturation and function of natural killer (NK) cells is important for understanding the antitumor immune response. Imianowski et al. show that the transcriptional regulator BACH2 is expressed in developing and mature NK cells and is a negative regulator of NK-cell maturation and function, keeping NK cells quiescent under conditions of IL15 stimulation. In mice lacking BACH2 in NK cells, the NK cells show increased cytotoxicity and enhanced ability to limit metastasis to the lungs in two preclinical models. The data provide new avenues for potential therapeutic modulation of NK cell–mediated antitumor immunity.Imianowski CJ, …, Roychoudhuri R. J Exp Med 2022 September 30;219:e20211476.

Tumor-associated macrophages related signature in glioma

Background: Glioma is the most common malignant primary tumor with a poor prognosis. Infiltration of tumor-associated macrophages (TAMs) is a hallmark of glioma. However, the regulatory mechanism of TAMs and the prognostic value of related signature in glioma remain unclear.Methods: TAMs were analyzed by EPIC, MCPCOUNTER and XCELL methods in multiple cohorts, including the TCGA merged GBMLGG, CGGA mRNAseq-325, and CGGA mRNAseq-693. Weighted correlation network analysis (WGCNA) were performed to identify candidate hub genes that might be related to TAMs. The prognostic genes were selected by Univariate Cox regression, Kaplan-Meier analysis and the least absolute shrinkage and selection operator (LASSO) multivariate Cox regression algorithm, and were used to construct a high efficacy prediction model.Results: Compared with LGG, TAMs of GBM in the TCGA merged GBMLGG, CGGA mRNAseq-693, and CGGA mRNAseq-325 cohorts were increased, and high TAMs levels predicted poorer overall survival for gliomas. The prediction model constructed by nine prognostic genes was highly efficient. The TAMs related risk-score was an independent risk factor for glioma. Moreover, high risk score was correlated with an increased population of TAMs in glioma, as well as the high immune scores, stromal scores and ESTIMATE scores.Conclusions: Increased TAMs might be an immune evasion mechanism of glioma. In addition, our findings suggested that TAMs-related signature was a valuable prognostic biomarker in glioma and provided therapeutic targets for glioma.

Tumor Associated Macrophages, as the Dominant Immune Cells, Are an Indispensable Target for Immunologically Cold Tumor-Glioma Therapy?

Tumor microenvironment (TME) is the cornerstone of the occurrence, development, invasion and diffusion of the malignant central nerve system (CNS) tumor, glioma. As the largest number of inflammatory cells in glioma TME, tumor associated macrophages (TAMs) and their secreted factors are indispensable to the progression of glioma, which is a well-known immunologically “cold” tumor, including the growth of tumor cells, invasion, migration, angiogenesis, cancer immunosuppression and metabolism. TAMs intimately interface with the treatment failure and poor prognosis of glioma patients, and their density increases with increasing glioma grade. Recently, great progress has been made in TAM-targeting for anti-tumor therapy. According to TAMs’ function in tumorigenesis and progression, the major anti-tumor treatment strategies targeting TAMs are to hinder macrophage recruitment in TME, reduce TAMs viability or remodel TAMs phenotype from M2 to M1. Different approaches offer unique and effective anti-tumor effect by regulating the phagocytosis, polarization and pro-tumor behaviors of macrophages in the therapy of glioma. The present review summarizes the significant characteristics and related mechanisms of TAMs and addresses the related research progress on targeting TAMs in glioma.

Long-lived tumor-associated macrophages in glioma.

BackgroundThe tumor microenvironment plays a major tumor-supportive role in glioma. In particular, tumor-associated macrophages (TAMs), which can make up to one-third of the tumor mass, actively support tumor growth, invasion, and angiogenesis. Predominantly alternatively activated (M2-polarized) TAMs are found in late-stage glioma in both human and mouse tumors, as well as in relapse samples from patients. However, whether tumor-educated M2 TAMs can actively contribute to the emergence and growth of relapse is currently debated.MethodsTo investigate whether tumor-educated stromal cells remaining in the brain after surgical removal of the primary tumor can be long-lived and retain their tumor-supporting function, we developed a transplantation mouse model and performed lineage-tracing.ResultsWe discovered that macrophages can survive transplantation and stay present in the tumor much longer than previously suggested, while sustaining an M2-polarized protumorigenic phenotype. Transplanted tumors showed a more aggressive growth and faster polarization of the TAMs toward an M2 phenotype compared with primary tumors, a process dependent on the presence of few cotransplanted macrophages.ConclusionsOverall, we propose a new way for tumor-educated TAMs to contribute to glioma aggressiveness by long survival and stable protumorigenic features. These properties could have a relapse-supporting effect.

NCMP-28. PTPRZ1-MET SIGNALING PROMOTES GLIOMA PROGRESSION THROUGH STIMULATION THE TRANSFORMATION FROM M1 TO M2 MACROPHAGE

Tumor-associated macrophages (TAMs) have multiple functions in both inhibiting or promoting diversity tumors progression and correlated with increased intratumoral heterogeneity. PTPRZ1-MET (ZM) fusion has been implicated in the development of glioma and recently associated with an unfavorable prognosis for afflicted secondary glioblastoma (sGBM) patients, as well as temozolomide chemoresistance. The underlying mechanisms of ZM fusion and TAM in glioma still remain undefined. SsGSEA is a rank-based method that computes an overexpression measure for a gene list of interest relative to all other genes in the genome. The ssGSEA scores for M1-type and M2-type macrophage scores are standardized across all tumor with known M1-type and M2-type macrophage properties in previous reports. The influence of ZM fusion on macrophage conversion in glioma was explored by performing gene set enrichment analysis and in vitro and in vivo experiments. An orthotopic xenograft model was established in this study. Here, we first show that the ssGSEA score of M2-type macrophage is upregulated in ZM fusion positively gliomas and M2-type macrophage score is highly associated with glioma patient overall survival. Further studies illustrated that the abundant macrophages populations and M1–M2 polarization of macrophage are tightly controlled processes of the hyper-activation of PTPRZ1-MET signaling in vitro and in orthotopic xenograft model. Meanwhile, our data also indicate that distinct transcriptional networks in brain-resident microglia and recruited bone-marrow-derived macrophages (BMDMs) are influenced by PTPRZ1-MET signaling pathway. These data indicate that PTPRZ1-MET signaling contribute to glioma malignant progression by recruiting macrophages and facilitating M2-type to M1-type macrophages conversion and therefore provide a novel therapeutic target for the treatment of sGBM patients.

RAGE: A novel target for breast cancer growth and metastasis.

Metastasis is a major cause of mortality in Breast Cancer (BC) patients in part due to lack of clinically established targeted therapies. Among the different types of BC, triple negative BC (TNBC) (ER-, PR-, HER2-) has been associated the most with poor prognosis and survival due to early metastasis to other organs and a lack of clinically established targeted therapies. Hence, elucidating novel mechanisms that regulate metastasis would lead to the development of targeted therapies and new treatments for TNBC and metastatic breast cancers. It is now well accepted that solid tumors, including those in the breast, have an inflammatory microenvironment. Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface molecules which has been associated with chronic inflammation, which in turn enhances the progression of various cancers [1]. We have shown that RAGE is expressed in a panel of aggressive BC cell lines and TNBC tissues [3]. High RAGE expression was also observed in lymph node and distant metastases patient samples. In addition, we observed that high RAGE expression was associated with poor prognosis in breast cancer [3]. RAGE has also been shown to play important role in various cancers including pancreatic cancer. Under hypoxic environment, RAGE was shown to interact directly to mutant KRAS and upregulate HIF1α that leads to the development of pancreatic cancer [2]. We have shown that RAGE deficiency inhibits the growth of murine breast cancer tumor cells [3]. RAGEdeficient mice have shown less chemically-induced inflammation [1]. Furthermore, we have shown that RAGE neutralizing antibody treatment significantly inhibited breast cancer metastasis in an intracardial mouse model [3]. RAGE is a multi-ligand receptor and binds to several inflammatory ligands such as advanced glycation end products (AGE), high mobility group box 1 peptide (HMGB-1), amyloid-β peptide and the S100 family of proteins. Our mechanistic investigation has revealed that RAGE mediates its functional effects in breast cancer by binding to S100A7 [3]. S100A7 is a small molecular weight calcium-binding protein [4]. Although a number of putative functions have been proposed for S100A7, its biological role, particularly in BC, remains to be defined [4]. Phylogenetic analyses have shown the mouse ancestor mS100a7a15 to be most related to human S100A7 [5]. It has been shown that mS100a7a15 is up-regulated during carcinogen-induced mammary tumorigenesis. However, the direct functional role of mS100a7a15 in disease progression is not well-characterized. We have shown that mS100a7a15 overexpression induced hyperplasia in mammary glands of these transgenic mice [5]. Upon binding to ligands, RAGE activates its downstream signaling mechanisms that augment and maintain chronic inflammatory conditions [1]. We have also shown that S100A7 enhances NF-kB activation and its nuclear translocation in TNBC cells. These features of RAGE make it an ideal candidate for therapeutic strategies against inflammation induced cancers. The link between inflammation and cancer has been postulated for a long time because of the presence of inflammatory cells in the tumor microenvironment, including myeloid cells and tumor associated macrophages (TAMs) [6]. These cells have been shown to significantly enhance tumor growth and the metastasis of various tumors and are key inhibitors of anti-tumor immunity [6]. In addition, collaborative interactions of tumor cells with TAMs have been associated with poor prognosis in BC [6]. TAMs have also been shown to play an important role in enhancing metastasis and drug resistance [6]. Therefore, inhibition of TAM accumulation and recruitment is a promising strategy for enhancing the effectiveness of immune-based therapies against tumors [6]. We and others have shown that RAGE is also expressed on immune cells [3, 5, 7]. RAGE expression was detected in different cell types present within the tumor microenvironment including macrophages. In addition, RAGE has been shown to be present in the microglia in the gliomas. Chen et al (2014) have shown that RAGE signaling in glioma TAMs regulates angiogenesis most likely by MMP9 [8]. We also showed in breast cancer mouse model that blocking of RAGE signaling significantly inhibited tumor growth, metastasis and angiogenesis through inhibition of MMP9+ TAMs [3]. In addition, RAGE also binds to S100A8/A9 to recruit myeloid derived suppressor cells (MDSCs) and thereby enhance cancer growth and metastasis [7]. These studies suggest that RAGE could enhance tumor growth and metastasis through regulating tumor microenvironment. Overall, our results indicate that RAGE could be used as a novel therapeutic target and biomarker for TNBCs. Furthermore RAGE/S100A7 signaling through paracrine and endocrine mechanisms in epithelial as well as TAMs plays an important role in linking inflammation to breast cancer development and metastasis (Fig. ​(Fig.1).1). In addition, RAGE also binds to S100A8/A9 to recruit myeloid derived suppressor cells (MDSCs) and thereby enhance breast cancer growth and metastasis. Figure 1 Role of S100A7/RAGE-signaling axis in breast cancer growth and metastasis

Tumor-Associated Macrophages in Glioma: Friend or Foe?

Tumor-associated macrophages (TAMs) contribute substantially to the tumor mass of gliomas and have been shown to play a major role in the creation of a tumor microenvironment that promotes tumor progression. Shortcomings of attempts at antiglioma immunotherapy may result from a failure to adequately address these effects. Emerging evidence supports an independent categorization of glioma TAMs as alternatively activated M2-type macrophages, in contrast to classically activated proinflammatory M1-type macrophages. These M2-type macrophages exert glioma-supportive effects through reduced anti-tumor functions, increased expression of immunosuppressive mediators, and nonimmune tumor promotion through expression of trophic and invasion-facilitating substances. Much of our work has demonstrated these features of glioma TAMs, and together with the supporting literature will be reviewed here. Additionally, the dynamics of glioma cell-TAM interaction over the course of tumor development remain poorly understood; our efforts to elucidate glioma cell-TAM dynamics are summarized. Finally, the molecular pathways which underlie M2-type TAM polarization and gene expression similarly require further investigation, and may present the most potent targets for immunotherapeutic intervention. Highlighting recent evidence implicating the transcription factor STAT3 in immunosuppressive tumorigenic glioma TAMs, we advocate for gene array-based approaches to identify yet unappreciated expression regulators and effector molecules important to M2-type glioma TAMs polarization and function within the glioma tumor microenvironment.