Tumor-Associated Microglia Secrete Extracellular ATP to Support Glioblastoma Progression
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ABSTRACT: Glioblastoma (GBM) is a highly aggressive brain tumor with poor prognosis and high recurrence rates. The complex immune microenvironment of GBM is highly infiltrated by tumor-associated microglia and macrophages (TAMs). TAMs are known to be heterogeneous in their functional and metabolic states and can transmit either pro-tumoral or anti-tumoral signals to glioma cells. Here, we performed bulk RNA-seq and single-cell RNA-seq on GBM patient samples, which revealed increased ATP synthase expression and oxidative phosphorylation (OXPHOS) activity in TAMs located in the tumor core relative to the tumor periphery. Both in vitro and in vivo models displayed similar trends of augmented TAM mitochondrial activity, along with elevated mitochondrial fission, glucose uptake, mitochondrial membrane potential, and extracellular ATP (eATP) production by TAMs in the presence of GBM cells. Tumor-secreted factors, including GM-CSF, induced the increase in TAM eATP production. Elevated eATP in the GBM microenvironment promoted glioma growth and invasion by activating the P2X purinoceptor 7 (P2X7R) on glioma cells. Inhibition of the eATP-P2X7R axis attenuated tumor cell viability in vitro and reduced tumor size and prolonged survival in glioma-bearing mouse models. Overall, this study revealed elevated TAM-derived eATP in GBM and provided the basis for targeting the eATP-P2X7R signaling axis as a therapeutic strategy in GBM.
Project description:Tumor-associated macrophages/microglia (TAMs) are prominent microenvironment components in human glioblastoma (GBM) that are potential targets for anti-tumor therapy. However, TAM depletion by CSF1R inhibition showed mixed results in clinical trials. We hypothesized that GBM subtype-specific tumor microenvironment convey distinct sensitivities to TAM targeting.We generated syngeneic PDGFB-driven and RAS-driven GBM models that resemble proneural-like and mesenchymal-like gliomas, and determined the effect of TAM targeting by CSF1R inhibitor PLX3397 on glioma growth. We also investigated the co-targeting of TAMs and angiogenesis on PLX3397-resistant RAS-driven GBM. Using single-cell transcriptomic profiling, we further explored differences in tumor microenvironment cellular compositions and functions in PDGFB- and RAS-driven gliomas. We found that growth of PDGFB-driven tumors was markedly inhibited by PLX3397. In contrast, depletion of TAMs at the early phase accelerated RAS-driven tumor growth and had no effects on other proneural and mesenchymal GBM models. In addition, PLX3397-resistant RAS-driven tumors did not respond to PI3K signaling inhibition. Single-cell transcriptomic profiling revealed that PDGFB-driven gliomas induced expansion and activation of pro-tumor microglia, whereas TAMs in mesenchymal RAS-driven GBM were enriched in pro-inflammatory and angiogenic signaling. Co-targeting of TAMs and angiogenesis decreased cell proliferation and changed the morphology of RAS-driven gliomas.Our work identify functionally distinct TAM subpopulations in the growth of different glioma subtypes. Notably, we uncover a potential responsiveness of resistant mesenchymal-like gliomas to combined anti-angiogenic therapy and CSF1R inhibition. These data highlight the importance of characterization of the microenvironment landscape in order to optimally stratify patients for TAM-targeted therapy.
Project description:Glioblastomas (GBMs) are highly invasive brain tumors replete with brain- and blood-derived macrophages, collectively known as tumor-associated macrophages (TAMs). Targeting TAMs has been proposed as a therapeutic strategy but has thus far yielded limited clinical success in slowing GBM progression, due in part to an incomplete understanding of TAM function in GBM. Here, by using an engineered hyaluronic acid-based 3D invasion platform, patient-derived GBM cells, and multi-omics analysis of GBM tumor microenvironments, we show that M2-polarized macrophages stimulate GBM stem cell (GSC) mesenchymal transition and invasion. We identify TAM-derived transforming growth factor beta induced (TGFβI/BIGH3) as a pro-tumorigenic factor in the GBM microenvironment. In GBM patients, BIGH3 mRNA expression correlates with poor patient prognosis and is highest in the most aggressive GBM molecular subtype. Inhibiting TAM-derived BIGH3 signaling with a blocking antibody or small molecule inhibitor suppresses GSC invasion. Our work highlights the utility of 3D in vitro tumor microenvironment platforms to investigate TAM-cancer cell crosstalk and offers new insights into TAM function to guide novel TAM-targeting therapies.
Project description:Glioblastoma (GBM) is the most common and malignant primary brain tumor. Although immunotherapy has shown promise in certain cancer types, it has not been effective against GBM, largely due to its highly immunosuppressive tumor microenvironment (TMEs), which is rich in tumor-associated macrophages/microglia (TAMs). TAMs in late-stage GBM contribute to T-cell exhaustion and worsen prognosis, but the role of TAMs in earlier stages of tumor development is unclear. By employing genetically engineered mouse models and human samples, we used spatiotemporal single-cell transcriptomics to investigate TAM evolution during GBM progression.
Project description:Clinical and experimental evidence indicates that tumor-associated macrophages (TAMs) promote malignant progression. In breast cancer, TAMs enhance tumor angiogenesis, tumor cell invasion, matrix remodeling, and immune suppression against the tumor. In this study, we examined late-stage mammary tumors from a transgenic mouse model of breast cancer. We used flow cytometry under conditions that minimized gene expression changes to isolate a rigorously defined TAM population previously shown to be associated with invasive carcinoma cells. The gene expression signature of this population was compared with a similar population derived from spleens of non-tumor-bearing mice using high-density oligonucleotide arrays. Using stringent selection criteria, transcript abundance of 460 genes was shown to be differentially regulated between the two populations. Bioinformatic analyses of known functions of these genes indicated that formerly ascribed TAM functions, including suppression of immune activation and matrix remodeling, as well as multiple mediators of tumor angiogenesis, were elevated in TAMs. Further bioinformatic analyses confirmed that a pure and valid TAM gene expression signature in mouse tumors could be used to assess expression of TAMs in human breast cancer. The data derived from these more physiologically relevant autochthonous tumors compared with previous studies in tumor xenografts suggest tactics by which TAMs may regulate tumor angiogenesis and thus provide a basis for exploring other transcriptional mediators of TAM trophic functions within the tumor microenvironment. Tumor-associated macrophages from late-stage mouse mammary tumors compared to splenic macrophages from non-tumor-bearing littermate controls. 4 biological replicates of each population were compared via gene expression arrays.
Project description:Glioblastoma multiforme (GBM) is the most aggressive form of glioma, and is notorious for its terminal prognosis and lack of responsiveness to current treatment approaches. The brain tumor microenvironment (TME) represents a largely untapped reservoir of therapeutic target options in GBM. Here we have focused on the interplay between glioma cells and tumor-associated macrophages/ microglia (TAMs). TAMs accumulate in the gliomas with disease progression, and depend on colony stimulating factor 1 receptor (CSF-1R) signaling for survival. In a recent study from our laboratory, mice bearing high-grade gliomas were treated with a CSF-1R inhibitor, BLZ945 (Novartis), and tumors regressed significantly after just 7 days of treatment (PMID: 24056773). Here we investigate whether long-term treatment of high-grade gliomas with BLZ945 would result in stable management of disease in a mouse model of proneural GBM. We show that ~44% of mice survived to the trial end point (EP) with minimal disease by MRI and histology, whereas ~56% of mice showed tumor recurrence (Reb). Serial transplantation of rebound tumor cells into naïve animals re-established BLZ945 responsiveness, suggesting a role for the microenvironment in supporting recurrent disease. Indeed, RNA-seq analysis on FACS purified tumor cells and TAMs from EP and Reb tumors showed elevated PI3K signaling in Reb tumors, driven by a heterotypic paracrine interaction between TAM-derived IGF-1 and tumor cell IGF-1R. We performed combination trials to block IGF-1R or downstream PI3K signaling in rebound tumors with BLZ945 treatment, and were able to significantly prolong overall survival. Given that CSF-1R inhibitors are currently in clinical trials for multiple cancer types including for GBM, understanding the molecular mechanisms that underlie non-responsive/ resistant tumors is timely and critical.
Project description:Therapies against glioblastoma multiforme (GBM) have been largely ineffective due to the infiltration of immunosuppressive tumor-associated macrophages (TAMs). Recent studies demonstrated that TAMs can also be immune-activating. However, markers differentiating these heterogeneous macrophage populations have not been established. In this study, we identified a subset of macrophages expressing CD169 that promote an anti-tumoral microenvironment in GBM. Using single-cell transcriptome analysis, we found that CD169+ macrophages in human and mouse gliomas produced proinflammatory chemokines, leading to the accumulation of T cells and NK cells. Depletion of CD169+ macrophages shortened the survival of mice with gliomas and reduced the function of antitumor lymphocytes. We show that IFN-γ produced by NK cells was critical for the accumulation of CD169+ macrophages into gliomas. Additionally, CD169 expression on macrophages increased the phagocytosis of apoptotic glioma cells. Our finding suggests that the CD169+ subset of TAMs promotes antitumor immune responses against GBM.
Project description:Therapies against glioblastoma multiforme (GBM) have been largely ineffective due to the infiltration of immunosuppressive tumor-associated macrophages (TAMs). Recent studies demonstrated that TAMs can also be immune-activating. However, markers differentiating these heterogeneous macrophage populations have not been established. In this study, we identified a subset of macrophages expressing CD169 that promote an anti-tumoral microenvironment in GBM. Using single-cell transcriptome analysis, we found that CD169+ macrophages in human and mouse gliomas produced proinflammatory chemokines, leading to the accumulation of T cells and NK cells. Depletion of CD169+ macrophages shortened the survival of mice with gliomas and reduced the function of antitumor lymphocytes. We show that IFN-γ produced by NK cells was critical for the accumulation of CD169+ macrophages into gliomas. Additionally, CD169 expression on macrophages increased the phagocytosis of apoptotic glioma cells. Our finding suggests that the CD169+ subset of TAMs promotes antitumor immune responses against GBM.
Project description:Therapies against glioblastoma multiforme (GBM) have been largely ineffective due to the infiltration of immunosuppressive tumor-associated macrophages (TAMs). Recent studies demonstrated that TAMs can also be immune-activating. However, markers differentiating these heterogeneous macrophage populations have not been established. In this study, we identified a subset of macrophages expressing CD169 that promote an anti-tumoral microenvironment in GBM. Using single-cell transcriptome analysis, we found that CD169+ macrophages in human and mouse gliomas produced proinflammatory chemokines, leading to the accumulation of T cells and NK cells. Depletion of CD169+ macrophages shortened the survival of mice with gliomas and reduced the function of antitumor lymphocytes. We show that IFN-γ produced by NK cells was critical for the accumulation of CD169+ macrophages into gliomas. Additionally, CD169 expression on macrophages increased the phagocytosis of apoptotic glioma cells. Our finding suggests that the CD169+ subset of TAMs promotes antitumor immune responses against GBM.
Project description:Glioblastoma (GBM) is a malignancy with a complex tumor microenvironment (TME) dominated by glioblastoma stem cells (GSCs) and infiltrated by tumor-associated macrophages (TAMs), and exhibits aberrant metabolic pathways. Lactate is a critical glycolytic metabolite that promotes tumor progression; however, the mechanisms of lactate transportation and lactylation in the tumor microenvironment (TME) of GBM remain elusive. Here, we found that the lactate metabolic signature was highly expressed in TAMs and tumor cells. Moreover, TAMs provide lactate to GSCs, promoting GSC proliferation and inducing lactylation of the non-homologous end joining (NHEJ) protein KU70 at the residue K317. TAM-derived lactate-mediated KU70 lactylation inhibits cGAS- type I interferon signaling, remodeling the immunosuppressive microenvironment through reduced cytotoxic CD8+ T cell infiltration, promoting the malignant progression of GBM. Combinatorial targeting of lactate transport and immune checkpoints demonstrated additive therapeutic benefit in immunocompetent orthotopic xenograft models. This study unveils TAM-derived lactate and lactylation as a critical regulator of NHEJ and create immunosuppressive microenvironment, linking the TME to DNA damage response in GBM and opening novel avenues for developing combinatorial therapy for GBM.
Project description:Glioblastoma multiforme (GBM), the most common and aggressive primary brain tumor in adults, can be divided into several molecular subtypes including proneural GBM. Most clinical strategies aimed at directly targeting glioma cells in these tumors have failed. A promising alternative is to target stromal cells in the brain microenvironment, such as tumor-associated microglia and macrophages (TAMs). Macrophages are dependent upon colony stimulating factor (CSF)-1 for differentiation and survival; therefore, we used an inhibitor of its receptor, CSF-1R, to target macrophages in a mouse proneural GBM model. CSF-1R inhibition dramatically increased survival in mice and regressed established GBMs. Tumor cell apoptosis was significantly increased, and proliferation and tumor grade markedly decreased. Surprisingly, TAMs were not depleted in tumors treated with the CSF-1R inhibitor. Instead, analysis of gene expression in TAMs isolated from treated tumors revealed a decrease in alternatively activated/ M2 macrophage markers, consistent with impaired tumor-promoting functions. These gene signatures were also associated with better survival specifically in the proneural subtype of patient gliomas. Collectively, these results establish macrophages as valid therapeutic targets in proneural gliomas, and highlight the clinical potential for CSF-1R inhibitors in GBM. RNA was isolated from sorted tumor associated macrophages (TAMs) from murine gliomas following either 7 days of vehicle or BLZ945 treatment. Samples were collected from 16 total tumor burdened mice, with 8 replicates for each treatment group. BLZ945: a Colony-Stimulating Factor 1 Receptor (CSF-1R) inhibitor