Targeting IRG1 in tumor-associated macrophages for cancer therapy
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ABSTRACT: Immune-responsive gene 1 (IRG1) is a mitochondrial aconitate decarboxylase and can produce the immunomodulatory metabolite itaconic acid (ITA). However, its role in modulating the function of tumor-associated macrophages (TAMs) remains elusive. Here, we show that IRG1 is expressed in TAMs in human tumors and mouse models of cancer. Tumor cells induce Irg1 expression in macrophages which dampens the inflammatory response and restricts M1-like TAM polarization. In contrast, Irg1-deficent macrophages acquire more proinflammatory M1-like features, promote immunogenic antigen presentation, and enhance cytotoxic T cell infiltration into tumor sites. Consequently, Irg1 deficiency suppresses the growth of mouse syngeneic tumors, including melanoma, colorectal cancer, breast cancer, and pancreatic cancer. Irg1-deficient macrophages not only dictate the tumoricidal effect but enhance the efficacy of anti-PD(L)1 immunotherapy. In conclusion, our data identify IRG1 as a myeloid immune check point gene and foster the development of genetic or pharmacologic targeting of IRG1 for skewing macrophages toward an anti-tumor phenotype to treat a broad spectrum of cancer.
Project description:Immune-response gene 1 (IRG1) transcription is rapidly induced by pathogen infections and inflammatory conditions primarily in cells of myeloid lineage. Deletion of Irg1 in mice causes severe defects in response to bacterial and viral infection and rapid death. IRG1 encodes a mitochondrial metabolic enzyme, aconitate decarboxylase 1 (ACOD1), that catalyzes the decarboxylation of cis-aconitate, a tricarboxylic acid cycle intermediate, to produce the anti-inflammatory metabolite itaconic acid (ITA). ITA can inhibit SDH5, resulting in elevated levels of succinate and metabolic reprogramming, or alkylate protein cysteine residues to induce electrophilic stress response mediated by NRF2 and IκBζ. Here we show that ITA is an antagonist of α-ketoglutarate (α-KG) and a potent inhibitor of α-KG/Fe2+-dependent TET family of DNA dioxygenases. In vitro, ITA binds to TET2 and inhibits the catalytic activity of TET2 and, reciprocally, α-KG blocks ITA binding to and inhibition of TET2. In vivo, lipopolysaccharides (LPS) treatment, which induces IRG1 expression and causes the intracellular accumulation of ITA, inhibits TET activity in Irg1-WT, but not Irg1-KO macrophages. Moreover, TET2 is a major target of ITA function in suppressing LPS-induced genes. LPS stimulates p65 NF-κB/RelA to bind with and recruit TET2 to hydroxymethylate and activate the Nfkbiz gene, which encodes IκBζ. Our results thus identify a physiological metabolite inhibitor of TET enzymes and reveal a novel mechanism for the anti-inflammatory function of ITA through dampening TET2-mediated NF-κB signaling.
Project description:Immunoresponsive gene 1 (IRG1) is one of the highest induced genes in macrophages under pro-inflammatory conditions and its function has been recently described: it codes for immune-responsive gene 1 protein/cis-aconitic acid decarboxylase (IRG1/CAD), an enzyme catalyzing the production of itaconic acid from cis-aconitic acid, a tricarboxylic acid (TCA) cycle intermediate. Itaconic acid possesses specific antimicrobial properties inhibiting isocitrate lyase, the first enzyme of the glyoxylate shunt, an anaplerotic pathway that bypasses the TCA cycle and enables bacteria to survive on limited carbon conditions. To elucidate the mechanisms underlying itaconic acid production through IRG1 induction in macrophages, we examined the transcriptional regulation of IRG1. Using a combination of literature information, transcription factor prediction models and genome-wide expression arrays, we inferred the regulatory network of IRG1 in mouse and human macrophages. 3 unstimulated (Control) and 3 LPS-stimulated human PBMC-derived macrophages
Project description:Immunoresponsive gene 1 (IRG1) is one of the highest induced genes in macrophages under pro-inflammatory conditions and its function has been recently described: it codes for immune-responsive gene 1 protein/cis-aconitic acid decarboxylase (IRG1/CAD), an enzyme catalyzing the production of itaconic acid from cis-aconitic acid, a tricarboxylic acid (TCA) cycle intermediate. Itaconic acid possesses specific antimicrobial properties inhibiting isocitrate lyase, the first enzyme of the glyoxylate shunt, an anaplerotic pathway that bypasses the TCA cycle and enables bacteria to survive on limited carbon conditions. To elucidate the mechanisms underlying itaconic acid production through IRG1 induction in macrophages, we examined the transcriptional regulation of IRG1. Using a combination of literature information, transcription factor prediction models and genome-wide expression arrays, we inferred the regulatory network of IRG1 in mouse and human macrophages. 3 unstimulated (Control) and 3 LPS-stimulated RAW 264.7 macrophages
Project description:Tumor-associated macrophages (TAMs) have immunosuppressive capacity in mouse models of cancer. Here we show that the genetic deletion of the microRNA (miRNA)-processing enzyme DICER in TAMs broadly programs them to a CD11c+MRC1â/low M1-like immunostimulatory phenotype characterized by activated interferon-γ (IFN-γ)/STAT1/IRF signaling. M1-like TAM programming fostered the recruitment of cytotoxic T-cells (CTLs), including tumor-antigen-specific CTLs, inhibited tumor growth, and enhanced the efficacy of PD1 checkpoint blockade. Bioinformatics analysis of TAM transcriptomes identified a limited set of miRNAs putatively involved in TAM programming. Re-expression of Let-7 in Dicer-deficient TAMs was sufficient to partly rescue the M2-like (protumoral) TAM phenotype and abate tumor CTL infiltration. Targeted suppression of DICER activity in TAMs may, therefore, stimulate antitumor immunity and enhance the efficacy of cancer immunotherapy. To explore the role of DICER in the development, activation and immunological functions of TAMs, we crossed homozygous LysM-Cre (Clausen et al., 1999) with Dicerlox/lox (Harfe et al., 2005) mice to obtain mice with myeloid-cell-specific Dicer1 gene deletion (LysM-Cre;Dicerâ/â, referred to as Dâ/â). These mice were then backcrossed to LysM-Cre to obtain the control LysM-Cre; Dicer+/+ mice (referred to as D+/+). Both LysM-Cre and Dicerlox/lox mutations were always homozygous in our experiment. We then inoculated Lewis lung carcinoma (LLC) cells subcutaneously (s.c.) in Dâ/â and control D+/+ mice. Once the tumors were established, we isolated by fluorescence-activated cell sorting (FACS) tumor-associated macrophages (F4/80+ cells).
Project description:Immunoresponsive gene 1 (IRG1) is one of the highest induced genes in macrophages under pro-inflammatory conditions and its function has been recently described: it codes for immune-responsive gene 1 protein/cis-aconitic acid decarboxylase (IRG1/CAD), an enzyme catalyzing the production of itaconic acid from cis-aconitic acid, a tricarboxylic acid (TCA) cycle intermediate. Itaconic acid possesses specific antimicrobial properties inhibiting isocitrate lyase, the first enzyme of the glyoxylate shunt, an anaplerotic pathway that bypasses the TCA cycle and enables bacteria to survive on limited carbon conditions. To elucidate the mechanisms underlying itaconic acid production through IRG1 induction in macrophages, we examined the transcriptional regulation of IRG1. Using a combination of literature information, transcription factor prediction models and genome-wide expression arrays, we inferred the regulatory network of IRG1 in mouse and human macrophages.
Project description:Immunoresponsive gene 1 (IRG1) is one of the highest induced genes in macrophages under pro-inflammatory conditions and its function has been recently described: it codes for immune-responsive gene 1 protein/cis-aconitic acid decarboxylase (IRG1/CAD), an enzyme catalyzing the production of itaconic acid from cis-aconitic acid, a tricarboxylic acid (TCA) cycle intermediate. Itaconic acid possesses specific antimicrobial properties inhibiting isocitrate lyase, the first enzyme of the glyoxylate shunt, an anaplerotic pathway that bypasses the TCA cycle and enables bacteria to survive on limited carbon conditions. To elucidate the mechanisms underlying itaconic acid production through IRG1 induction in macrophages, we examined the transcriptional regulation of IRG1. Using a combination of literature information, transcription factor prediction models and genome-wide expression arrays, we inferred the regulatory network of IRG1 in mouse and human macrophages.
Project description:Tumor immunotherapy has been convincingly demonstrated as a feasible approach for treating cancers. Although promising, however, the immunosuppressive tumor microenvironment (TME) has been recognized as a major obstacle in tumor immunotherapy. It is highly desirable to release an immunosuppressive “brake” for improving cancer immunotherapy. Among tumor-infiltrated immune cells, tumor-associated macrophages (TAMs) play an important role in the growth, invasion and metastasis of tumors. The polarization of TAMs (M2) into the M1 type can alleviate the immunosuppression of the TME and enhance the effect of immunotherapy. Inspired by this, we constructed a therapeutic exosomal vaccine from antigen-stimulated M1-type macrophages (M1OVA-Exos). M1OVA-Exos are capable of polarizing TAMs into M1 type through downregulation of the Wnt signaling pathway. Mediating the TME further activates the immune response and inhibits tumor growth and metastasis via the exosomal vaccine. Our study provides a new strategy for the polarization of TAMs, which augments cancer vaccine therapy efficacy.
Project description:The main challenge for immune checkpoint blockade (ICB) therapy lies in immunosuppressive tumor microenvironment (TME). Repolarizing M2-like tumor-associated macrophages (TAMs) into inflammatory M1 phenotype is a promising strategy for cancer immunotherapy. Here, we found that the transmembrane protein SHISA3 is induced by DAMPs/PAMPs in macrophages via nuclear factor-κB (NF-κB) transcription factors, and SHISA3 forms complex with HSPA8 to reciprocally activates NF-κB signaling thus maintains M1 polarization of macrophages. Enforced expression of Shisa3 in TAMs increases their phagocytosis and antigen presentation abilities and promotes CD8+ T cell-mediated antitumor immunity. Local delivery of mRNA encoding Shisa3 enables therapy of cancer by dual effects on tumor cells and TAMs, and enhance the efficacy of PD-1 antibody. Taken together, our findings describe the role of SHISA3 in reprogramming TAMs that ameliorates cancer immunotherapy To find new molecules that regulate macrophage polarization, we performed transcriptomic analysis on early macrophages polarization induced by LPS for 0, 2, 4 hours.
Project description:Tumor metabolic reprogramming has been recognized as a critical determinant in tumor development and cancer immunotherapy. Aberrant choline metabolism is emerging as a defining hallmark of cancer. However, its impact on antitumor immunity remains largely unclear. Carbohydrate responsive element binding protein (ChREBP)-mediated choline deprivation impels tumor-associated macrophages (TAMs) reprogramming and maintains an immunosuppressive tumor microenvironment (TME). Mechanistically, ChREBP interacts with SP1 to increase the expression of immunosuppressive chemokines CCL2 and CXCL1, as well as choline transporter SLC44A1. As such, high expression of CCL2 and CXCL1 expression promotes recruitment of TAMs and MDSCs in the TME. Tumor cells with high SLC44A1 expression compete consuming choline with M1-like TAMs, inhibiting cGAS-STING signaling and promoting the polarization of M1 to M2 macrophages. Clinically, ChREBP-SP1-choline metabolism axis expression is associated with poor clinical outcome in CRC. Inhibiting ChREBP reduces M2-like TAMs and MDSCs to enhance anti-tumor immunity, suggesting ChREBP as a potential immunotherapy target in cancer.
Project description:Tumor-associated macrophages (TAMs) have immunosuppressive capacity in mouse models of cancer. Here we show that the genetic deletion of the microRNA (miRNA)-processing enzyme DICER in TAMs broadly programs them to a CD11c+MRC1−/low M1-like immunostimulatory phenotype characterized by activated interferon-γ (IFN-γ)/STAT1/IRF signaling. M1-like TAM programming fostered the recruitment of cytotoxic T-cells (CTLs), including tumor-antigen-specific CTLs, inhibited tumor growth, and enhanced the efficacy of PD1 checkpoint blockade. Bioinformatics analysis of TAM transcriptomes identified a limited set of miRNAs putatively involved in TAM programming. Re-expression of Let-7 in Dicer-deficient TAMs was sufficient to partly rescue the M2-like (protumoral) TAM phenotype and abate tumor CTL infiltration. Targeted suppression of DICER activity in TAMs may, therefore, stimulate antitumor immunity and enhance the efficacy of cancer immunotherapy.