Lack of TREM2 during anti-PD-1 therapy reprograms intestinal macrophages and microbiota to enhance tumor rejection
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ABSTRACT: The gut microbiota and tumor-associated macrophages (TAM) impact anti-PD-1 checkpoint blockade. Reprogramming TAM by either blocking or deleting the macrophage receptor TREM2 attenuates tumor growth, and lack of functional TREM2 enhances tumor elimination by anti-PD-1. Here, we found that anti-PD-1 combined with TREM2 deficiency induces proinflammatory programs in intestinal macrophages and a concomitant expansion of Ruminococcus gnavus (R. gnavus) in the gut microbiota. Gavage of wild-type mice with R. gnavus recapitulated enhancement of anti-PD-1-mediated tumor elimination occurring in the absence of TREM2. The intestinal proinflammatory environment coincided with expansion, increased circulation and migration of TNF-producing CD4+ T cells to the tumor bed. Thus, TREM2 remotely controls anti-PD-1 checkpoint blockade through modulation of the intestinal immune environment and microbiota, with R. gnavus emerging as a potential probiotic agent for increasing responsiveness to anti-PD-1.
Project description:The prevailing view is that myeloid cells in the tumor microenvironment (TME) are immunosuppressive and promote glioblastoma (GBM) progression. However, myeloid cells have the functional plasticity to restrict or support tumor cell growth. TREM2 plays important roles in brain microglial function in neurodegenerative diseases, but the role of TREM2 in the GBM TME has not been examined. We found TREM2 is highly expressed in myeloid subsets, including macrophages and microglia in human and mouse GBM tumors and that high TREM2 expression correlates with poor prognosis in GBM patients. TREM2 loss of function in human macrophages and mouse myeloid cells increased tumoricidal capacity. TREM2 in myeloid cells restricts IFNγ-induced immunoactivation and proinflammatory polarization. In orthotopic mouse GBM models, Trem2-/- mice and mice with acute brain Trem2 reduction demonstrate survival benefit. Trem2 inhibition reprograms myeloid phenotypes and increases PD-1+CD8+ T cells in the TME. Trem2 deficiency enhances the effectiveness of anti-PD-1 treatment and may represent a therapeutic strategy for GBM patients.
Project description:The prevailing view is that myeloid cells in the tumor microenvironment (TME) are immunosuppressive and promote glioblastoma (GBM) progression. However, myeloid cells have the functional plasticity to restrict or support tumor cell growth. TREM2 plays important roles in brain microglial function in neurodegenerative diseases, but the role of TREM2 in the GBM TME has not been examined. We found TREM2 is highly expressed in myeloid subsets, including macrophages and microglia in human and mouse GBM tumors and that high TREM2 expression correlates with poor prognosis in GBM patients. TREM2 loss of function in human macrophages and mouse myeloid cells increased tumoricidal capacity. TREM2 in myeloid cells restricts IFNγ-induced immunoactivation and proinflammatory polarization. In orthotopic mouse GBM models, Trem2-/- mice and mice with acute brain Trem2 reduction demonstrate survival benefit. Trem2 inhibition reprograms myeloid phenotypes and increases PD-1+CD8+ T cells in the TME. Trem2 deficiency enhances the effectiveness of anti-PD-1 treatment and may represent a therapeutic strategy for GBM patients.
Project description:Studying host-microbiota interactions is fundamental to understand mechanisms involved in intestinal inflammation and inflammatory bowel diseases. In this work, we studied these interactions in mice mono-associated with 4 bacteria and 2 yeasts, all representative of intestinal microbiota and/or associated with IBD pathogenesis: Bacteroides thetaiotaomicron, adhesive-invasive Escherichia coli (AIEC), Ruminococcus gnavus, Roseburia intestinalis, Saccharomyces boulardii and Candida albicans. Transcriptomics analyses showed that B. thetaiotaomicron had the highest immunological effect, being able to almost recapitulate the effects of a whole microbiota, and particularly induced Treg pathways. Furthermore, this analysis also pointed out the effects of E. coli AIEC LF82 on IDO activation and of S. boulardii on angiogenesis, as well as major effects of R. gnavus on metabolism. This work therefore reveals information on the role of each micro-organism and proposes several tracks to follow to better understand IBD pathogenesis and identify therapeutic targets 6 mono-associations + 2 controls (germ-free and conventionalized mice), with 5 to 7 mice per group.
Project description:Checkpoint immunotherapy unleashes T cell effector functions that control tumor growth, but can be undermined by myeloid cells that induce immunosuppression. TREM2 is a myeloid surface receptor that binds lipids and transmits intracellular signals through protein-tyrosine phosphorylation known to sustain microglial responses during Alzheimer’s disease. Intriguingly, TREM2 expression has recently been noted in tumor-infiltrating macrophages. We found that Trem2–/– mice are more resistant to growth of sarcoma, colorectal and mammary cancer cells than wild-type mice and are more responsive to anti-PD-1 immunotherapy. Furthermore, treatment with anti-TREM2 mAb curbed tumor growth and led to complete tumor regression when combined with anti-PD-1. scRNA-seq revealed that both constitutive TREM2 deficiency and anti-TREM2 are associated with relatively scant representation of MRC1+ and CX3CR1+ subsets in the macrophage tumor infiltrate, paralleled by expansion of subsets expressing immunostimulatory molecules. These changes were associated with improved T cell responses. TREM2 expression was evident in tumor macrophages in over 200 human cancer cases examined and inversely correlated with prolonged survival for two types of cancer. Thus, TREM2 is a promising target to modify tumor-infiltrating myeloid cells and effectively augment checkpoint immunotherapy.
Project description:Studying host-microbiota interactions is fundamental to understand mechanisms involved in intestinal inflammation and inflammatory bowel diseases. In this work, we studied these interactions in mice mono-associated with 4 bacteria and 2 yeasts, all representative of intestinal microbiota and/or associated with IBD pathogenesis: Bacteroides thetaiotaomicron, adhesive-invasive Escherichia coli (AIEC), Ruminococcus gnavus, Roseburia intestinalis, Saccharomyces boulardii and Candida albicans. Transcriptomics analyses showed that B. thetaiotaomicron had the highest immunological effect, being able to almost recapitulate the effects of a whole microbiota, and particularly induced Treg pathways. Furthermore, this analysis also pointed out the effects of E. coli AIEC LF82 on IDO activation and of S. boulardii on angiogenesis, as well as major effects of R. gnavus on metabolism. This work therefore reveals information on the role of each micro-organism and proposes several tracks to follow to better understand IBD pathogenesis and identify therapeutic targets
Project description:Immune checkpoint inhibitors (CPIs) have revolutionised cancer treatment, with previously untreatable disease now amenable to potential cure. Combination regimens of anti-CTLA-4 and anti-PD-1 show enhanced efficacy but are prone to off-target immune-mediated tissue injury, particularly at the barrier surfaces. CPI-induced colitis is a common and serious complication. To probe the impact of immune checkpoints on intestinal homeostasis, mice were challenged with anti-CTLA-4 and anti-PD-1 immunotherapy and manipulation of the intestinal microbiota. Colonic immune responses were profiled using bulk RNA-sequencing.
Project description:Paneth cells are the primary, and possibly the sole, source of lysozyme in the intestinal lumen. Mice lacking the Paneth cell lysozyme gene, Lyz1, had diminished NLR signaling and basal inflammation, and were further protected from experimental colitis. Protection depended on an enhanced goblet and tuft cell program that was driven by IL13-IL4Ra-Stat6 signaling and required an expansion of lysozyme-sensitive mucolytic bacteria. Forced ectopic lysozyme production in colonic epithelium suppressed these bacteria and exacerbated colitis. Single cell RNA-seq of Lyz1 KO lamina propria revealed an activated ILC2 profile towards cytokine production. One lysozymesensitive species, Ruminococcus gnavus , when processed by lysozyme, induced a pro-inflammatory response, while non-processed R. gnavus stimulated IL13 production in lymphocytes. Consistent with a role of lysozyme for cell-wall processing in the inflammatory response, Lyz1 KO microbiota was anti-colitogenic in lysozymedeficient hosts but colitogenic in lysozyme-sufficient hosts. Thus, Paneth cell lysozyme regulates inflammatory tone by modulating mucosal response to specific bacterial groups.
Project description:The gut microbiome modulates immunotherapy treatment responses, and this may explain why immune checkpoint inhibitors (ICI), such as anti-PD-1, are only effective in some patients. Previous studies correlated lipopolysaccharide (LPS)-producing gut microbes with poorer prognosis; however, LPS from diverse bacterial species can range from immunostimulatory to inhibitory. By functionally analyzing fecal metagenomes from 112 melanoma patients, we found that a subset of LPS-producing bacteria encoding immunostimulatory hexa-acylated LPS was enriched in microbiomes of clinical responders. In an implanted tumor mouse model of anti-PD-1 treatment, microbiota-derived hexa-acylated LPS was required for effective anti-tumor immune responses, and LPS-binding antibiotics and a small molecule TLR4 antagonist abolished anti-PD-1 efficacy. Conversely, oral administration of hexa-acylated LPS to mice significantly augmented anti-PD-1-mediated anti-tumor immunity. Penta-acylated LPS did not improve anti-PD-1 efficacy in vivo and inhibited hexa-acylated LPS-induced immune activation in vitro. Microbiome hexa-acylated LPS therefore represents an accessible predictor and potential enhancer of immunotherapy responses.