Indoleamine 2,3-dioxygenase 1 Upregulation Research Articles

Abstract 3963: Indoleamine 2,3-dioxygenase 1 (IDO1) regulates immune evasion in lymphoma

Abstract Recently, anti-programmed death (anti-PD) therapy has been at the forefront of cancer therapy. However, the clinical efficacy of anti-PD therapy in DLBCL remains obscure. The marginal response to anti-PD therapy in DLBCL indicates that different mechanisms of immune evasion other than the PD-1/PD-L1 pathway may be present. To investigate the mechanisms of resistance to anti-PD therapy in DLBCL, we assessed gene expression in patients with DLBCL in public database. Accordingly, we found indoleamine 2,3-dioxygenase 1 (IDO1), a key enzyme responsible for tryptophan catabolism, is highly expressed in DLBCL. IDO1 expression is upregulated by IFN-gamma produced by T cells in tumor microenvironments (TMEs) of various cancer types. Upregulated IDO1 leads to the production of kynurenine, which creates an immunosuppressive TMEs. However, it remains unknown whether IDO1 induces immune evasion in DLBCL and if so, which subsets of IDO1 expressing cells are responsible for immune evasion in DLBCL. To address these questions, we first determined the intrinsic role of IDO1 in lymphoma cells. We knocked down IDO1 expression (IDO1 KD) in a human DLBCL RC-K8 cell line using short hairpin RNA. We observed decreased cell proliferation in IDO KD lymphoma cells compared with control cells. We also found increased susceptibility to apoptosis in IDO1 KD RC-K8 cells compared with IDO1 WT control, when these were co-cultured with THP-1-derived macrophages or activated Jurkat T lymphocytes. These data suggest that lymphoma IDO1 has an intrinsic role of lymphoma progression and makes lymphoma sensitive to cytotoxic immune cells. To validate the anti-tumor effect of IDO1 deficiency in immune cells, we assessed EL4 lymphoma growth and immune TME of lymphoma in syngeneic wild type (WT) and Ido1 knock-out (KO) mice. The growth of EL4 lymphoma tumor was significantly suppressed in Ido1 KO mice compared to WT mice (Ido1 KO: 621.9mm3 vs WT: 1228mm3, N=22, P<0.001). Immune TME assessment revealed a decreased frequency of regulatory T cells, yet, the increased proportions of B cells, MHC II+ antigen-presenting cells, monocytes, and NK cells in Ido1 KO tumors compared with WT control. In summary, IDO1 is highly expressed in DLBCL. IDO1 up-regulation may drive lymphoma progression both intrinsically and extrinsically (immune evasion). This data suggests that IDO1 overexpression may be one of the mechanisms of resistance to anti-PD therapy. We will extend our studies to determine a combination effect of IDO1 inhibitors with immune checkpoint inhibitors including anti-PD therapy in DLBCL. Citation Format: Jihyun Park, Seung-Joo Yoo, Qianni Hu, Carly M. Fielder, Hyundong Yoon, Junshik Hong, Byung-Su Kim, Youngil Koh, Tae Kon Kim, Sung-Soo Yoon, Chi Yan. Indoleamine 2,3-dioxygenase 1 (IDO1) regulates immune evasion in lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3963.

Radiation fractionation effect on IDO1 through NF-kB/COX2 axis in non-small cell lung cancer.

e20613 Background: Lung cancer is the leading cancer mortality worldwide. Radiotherapy(RT) plays an important role in lung cancer treatment. Different does fractionation of RT has different effects on the prognosis of lung cancer. For example, stereotactic body radiotherapy can significantly improve the prognosis compared with conventionally Fractionated Radiotherapy. In non-small cell lung cancer, we have previously shown that Indoleamine 2,3-dioxygenase 1 (IDO1) metabolites and radiation induced changes had significant effects on long-term survival in patients treated with either Stereotactic body Radiation Therapy of 10Gy fraction size or conventional fractionated radiotherapy of 2Gy fraction size. However, the underlining molecular mechanism is unknown. In this study, we aimed to elaborate the molecular mechanism of such clinical differential effects in the laboratory. Methods: This study applied two dose/fractionation regimens with a similar BED10: 10Gyx1 and 2Gyx8. 10Gyx1 and 2Gyx8 were tested in cell lines of A549, H1299, Calu-1, TC-1 of human and murine NSCLC as well as normal rat cardiomyocyte cell line H9c2, and in vivo (TC-1 implanted C57Bl/6 mice). The mRNA and protein levels of IDO1, p-NF-kB, COX2 from cells and tumor tissues were determined by using qPCR, western blot and immunohistochemistry. Survival outcome was tested by colony formation assay in vitro and tumor growth curve in vivo. Results: In vitro, 10Gyx1 and 2Gyx8 induced IDO1 expression in all tested cell lines and the level of IDO1 expression induced by 10Gyx1 was lower than 2Gyx8. Both 10Gyx1 and 2Gyx8 increased p-NF-kB and COX2 expression and the level induced by 10Gyx1 was lower than 2Gyx8. In tumor bearing mice, two dose/fractionation regimens also induced intratumor IDO1 expression and increased the levels of p-NF-kB and COX2. Interestingly, the increased levels of IDO1, p-NF-kB, COX2 after 10Gyx1 were also significantly lower than 2Gyx8 in vivo. IDO inhibitor synergized with RT and enhanced cell killing efficacy of RT. Conclusions: The findings of this study suggest different does fractionation of RT induced up-regulation of IDO1 through NF-kB/COX2 axis in NSCLC and non-cancerous cell lines, what’s more, hypofractionated radiotherapy 10Gyx1 had less upregulation that of conventionally fractionated radiotherapy 2Gy x8 on IDO1 immune inhibitory pathway. The finding of hypofractionated radiotherapy less immune suppression differ from the traditional belief of more immune stimulation. Our current study provides a rationale in using IDO1 as a biomarker to design RT dose fractionation and/or immunotherapy in combination and possibilities for clinical trials to design IDO1 inhibitors in combination with radiotherapy.

Indoleamine 2,3-dioxygenase 1 in circumventing checkpoint inhibitor responses: Updated.

Metabolic alterations occur commonly in tumor cells as a way to adapt available energetic sources for their proliferation, survival and resistance. Indoleamine 2,3-dioxygenase 1 (IDO1) is an intracellular enzyme catalyzing tryptophan degradation into kynurenine. IDO1 expression shows a rise in the stroma of many types of human cancers, and it provides a negative feedback mechanism for cancer evasion from immunosurveillance. Upregulation of IDO1 correlates with cancer aggression, poor prognosis and shortened patient survival. The increased activity of this endogenous checkpoint impairs effector T cell function, increases regulatory T cell (Treg) population and induces immune tolerance, so its inhibition potentiates anti-tumor immune responses and reshapes immunogenic state of tumor microenvironment (TME) presumably through normalizing effector T cell activity. A point is that the expression of this immunoregulatory marker is upregulated after immune checkpoint inhibitor (ICI) therapy, and that it has inducible effect on expression of other checkpoints. These are indicative of the importance of IDO1 as an attractive immunotherapeutic target and rationalizing combination of IDO1 inhibitors with ICI drugs in patients with advanced solid cancers. In this review, we aimed to discuss about the impact of IDO1 on tumor immune ecosystem, and the IDO1-mediated bypass of ICI therapy. The efficacy of IDO1 inhibitor therapy in combination with ICIs in advanced/metastatic solid tumors is also a focus of this paper.

Modulation of Indoleamine 2,3-Dioxygenase 1 During Inflammatory Bowel Disease Activity in Humans and Mice.

Indoleamine 2,3 dioxygenase-1 (IDO1), a key enzyme in tryptophan metabolism, is strongly up-regulated both in human inflammatory bowel disease (IBD) and animal models of colitis, however its role in the pathogenesis is still controversial. In this study, we investigated IDO1 expression and activity in a mouse model of DSS-induced chronic colitis as well as in colon biopsies and sera from IBD patients. Chronic colitis was induced in mice through the oral administration of dextran sodium sulfate (DSS), and IDO1 activity was induced by i.p. treatment with N-acetyl serotonin (NAS). IDO1 expression and catalytic activity (measured as Kyn/Trp ratio) was evaluated in sera and tissue samples collected from mice and 93 IBD patients under immunotherapy with Vedolizumab (VDZ) or Ustekinumab (UST). Strong up-regulation of IDO1 was found in colons of mice with acute colitis, which follows disease activity. Enhanced IDO1 activity by NAS treatment protects the intestinal mucosa during the recovery phase of chronic colitis. In IBD patients, IDO1 expression and activity correlate with the severity of mucosal inflammation with inflamed regions showing higher IDO1 expression compared to non-inflamed regions within the same patient. Endoscopic response to VDZ/UST treatment is associated with decreased expression of IDO1. This is the first study demonstrating immunomodulatory activity of IDO1 in a chronic mouse model of DSS-induced colitis. As its expression and catalytic activity correlate with the grade of mucosal inflammation and treatment response, IDO1 could represent a promising biomarker for disease severity and treatment monitoring in IBD.

Molecular mechanisms involved in the IL-6-mediated upregulation of indoleamine 2,3-dioxygenase 1 (IDO1) expression in the chorionic villi and decidua of women in early pregnancy

BackgroundIL-6 induces the upregulation of indoleamine 2,3-dioxygenase (IDO1) at the maternal-foetal interface, but the regulation mechanisms of IDO1 by IL-6 at this interface have not been fully understood.MethodsWestern blotting, qRT–PCR and/or immunohistochemistry were employed to measure the expression of IDO1, IL-6, SHP-1/2, SOCS3 and STAT3/p (STAT3 and pSTAT3) in tissues of chorionic villi and decidua (TCVD) in vivo and in cultured TCVD that were treated with IL-6 in the presence or absence of an IL-6 inhibitor.ResultsMutually positive relationships among the protein levels of IL-6, IDO1, SHP-1/2 and STAT3/p was observed, and the expression of IDO1, SHP-1/2 and STAT3/p was increased in a dose-dependent manner in TCVD in vivo and in cultured TCVD treated with IL-6 at increasing concentrations (0–100 ng/ml). The level of IL-6 was negatively related to SOCS3 level in TCVD. The expression of SOCS3 was increased in a dose-dependent manner, and SOCS3 level was positively correlated with SHP-1, SHP-2 and STAT3/p level in cultured TCVD treated with 0–2 ng/ml IL-6; however, opposite results were observed after treatment with 2–100 ng/ml IL-6. The IL-6-induced upregulation of IDO1, SHP-1, SHP-2 and STAT3/p expression could be reversed, while the IL-6-induced upregulation of SOCS3 expression was exacerbated by Corylifol A.ConclusionsIn normal pregnancy, IL-6 upregulates the expression of IDO1 by promoting SHP-1/2 expression via STAT3/p and simultaneously negatively regulates the expression of SOCS3. High expression of IL-6 causes the upregulation of IDO1 expression and the downregulation of SOCS-3 expression, which may be beneficial for maintaining immunological tolerance.

Tobacco carcinogen induces tryptophan metabolism and immune suppression via induction of indoleamine 2,3-dioxygenase 1

Indoleamine 2,3-dioxygenase 1 (IDO1), the enzyme that catabolizes tryptophan (Trp) metabolism to promote regulatory T cells (Tregs) and suppress CD8+ T cells, is regulated by several intrinsic signaling pathways. Here, we found that tobacco smoke, a major public health concern that kills 8 million people each year worldwide, induced IDO1 in normal and malignant lung epithelial cells in vitro and in vivo. The carcinogen nicotine-derived nitrosaminoketone (NNK) was the tobacco compound that upregulated IDO1 via activation of the transcription factor c-Jun, which has a binding site for the IDO1 promoter. The NNK receptor α7 nicotinic acetylcholine receptor (α7nAChR) was required for NNK-induced c-Jun activation and IDO1 upregulation. In A/J mice, NNK reduced CD8+ T cells and increased Tregs. Clinically, smoker patients with non-small-cell lung cancer (NSCLC) exhibited high IDO1 levels and low Trp/kynurenine (Kyn) ratios. In NSCLC patients, smokers with lower IDO1 responded better to anti-PD1 antibody treatment than those with higher IDO1. These data indicate that tobacco smoke induces IDO1 to catabolize Trp metabolism and immune suppression to promote carcinogenesis, and lower IDO1 might be a potential biomarker for anti-PD1 antibodies in smoker patients, whereas IDO1-high smoker patients might benefit from IDO1 inhibitors in combination with anti-PD1 antibodies.

Abstract 5884: Comprehensive analyzing the expression of IDO1 and TDO2 in bladder cancer

Abstract Background: Several lines of evidence have been focused on the roles of tryptophan metabolism genes like indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO2) in bladder cancer progression. However, the alternative way of targeting in cancer immunotherapy has been not yet investigated in bladder cancer. Method: We explored and validated the clinicopathological significance and the correlation with immune infiltrates of IDO1 and TDO2 expression in bladder cancer using Bladder urothelial carcinoma (BLCA) and other Gene Expression Omnibus (GEO) datasets (GSE13570, GSE31684, GSE48277) downloaded from https://xenabrowser.net/ and https://www.ncbi.nlm.nih.gov/geo/. The correlation between IDO1, TDO2 expression and the immune infiltrates as well as PD-L1 gene expression in BLCA dataset was explored with TIMER2.0, http://timer.comp-genomics.org/. Immunohistochemistry was performed to validate the relationship between TDO2 and PD-L1 expression in bladder cancer. Results: We figured out the IDO1 and TDO2 expressions were significantly upregulated in basal type compared with other molecular subtypes in BLCA. P53 mutations were associated with upregulation of IDO1 and TDO2 expression (p<0.01) whereas FGFR3 mutation was associated with downregulation of IDO1 and TDO2 expression (p<0.001). The overexpression of IDO1, TDO2 overexpression was significantly associated with advanced disease in BC. IDO1 and TDO2 expression were significantly correlated with purity and immune cell infiltrates, including T cells CD8+, T cells CD4+, B cells, neutrophils, and macrophages as wells as myeloid dendritic cells. Interestingly, TDO2 were positively correlated with cancer-associated fibroblasts (CAFs) (rho=0.5, p=1.14e-24). PD-L1 expression was also correlated with IDO1 (rho=0.64, p=4.42e-49) and TDO2 expression (rho=0.42, p=5.01e-19). Immunohistochemistry revealed the correlation between TDO2 and PD-L1 expression (p=0.011). Conclusion: Our results pointed out that IDO1 and TDO2 could play an essential role in regulating the tumor microenvironment as well as immune tolerance in bladder cancer. Suggesting that IDO1, TDO2 might be a promising novel immunotherapy target for bladder cancer patients. Citation Format: Quoc Thang Pham, Thanh Tu Nguyen, Thao Quyen Nguyen, Duc Tung Luu, Thi Nhu Diem Pham, Thi Thanh Tam Bui, Thanh Tu Duong, Dang Anh Thu Phan, Quoc Dat Ngo. Comprehensive analyzing the expression of IDO1 and TDO2 in bladder cancer [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 5884.

Clinical Relevance of Serum Kyn/Trp Ratio and Basal and IFNγ-Upregulated IDO1 Expression in Peripheral Monocytes in Early Stage Melanoma.

Immune escape is an early phenomenon in cancer development/progression. Indoleamine 2,3-dioxygenase 1 (IDO1) is a normal endogenous mechanism of acquired peripheral immune tolerance and may therefore be tumor-promoting. This study investigated the clinical relevance of IDO1 expression by immune cells in the lymph nodes and blood and of the serum kynurenine/tryptophan (Kyn/Trp) ratio in 65 systemic treatment naïve stage I-III melanoma patients. Blood samples were collected within the first year of diagnosis. Patients had a median follow-up of 61 months. High basal IDO1 expression in peripheral monocytes and low IFNγ-induced IDO1 upregulation correlated with worse outcome independent from disease stage. Interestingly studied factors were not interrelated. During follow-up, the risk of relapse was 9% (2/22) in the subgroup with high IFNγ-induced IDO1 upregulation in monocytes. In contrast, if IDO1 upregulation was low, relapse occurred in 30% (3/10) of patients with low basal IDO1 expression in monocytes and in 61.5% (8/13) in the subgroup with high basal IDO1 expression in monocytes (Log-Rank test, p=0.008). This study reveals some immune features in the blood of early stage melanoma that may be of relevance for disease outcome. These may offer a target for sub-stratification and early intervention.

GCH1 induces immunosuppression through metabolic reprogramming and IDO1 upregulation in triple-negative breast cancer

PurposeRegulatory T cells (Tregs) heavily infiltrate triple-negative breast cancer (TNBC), and their accumulation is affected by the metabolic reprogramming in cancer cells. In the present study, we sought to identify...

Inhibition of indoleamine 2,3-dioxygenase 1 synergizes with oxaliplatin for efficient colorectal cancer therapy

We investigated the immunogenic cell death provoked by oxaliplatin (OXA) and the involvement of OXA-induced immunosuppression in colorectal cancer. Immune-proficient or -deficient mice were employed to evaluate the therapeutic effects of OXA. Immunogenic cell death was characterized by cell-surface calreticulin, cytosol-translocated high migration rate group protein B1 (HMGB1), and secretory ATP content. Bone marrow-derived dendritic cell (BMDC) maturation and CD8+ T cell expansion were measured by flow cytometry. Expression of immunosuppressive genes was quantified by both RT-PCR and western blots. The proliferative and apoptotic indexes of xenograft tumors were evaluated by immunohistochemistry and TUNEL assays, respectively. The secretory cytokines were measured with ELISA. OXA induced immunogenic cell death of murine colorectal cancer, which greatly depended on the host immune response. OXA-pretreated CT26 cells promoted BMDC maturation and CD8+ T cell expansion. OXA significantly upregulated indoleamine 2,3-dioxygenase 1 (IDO1) in patient-derived colorectal cancer cells and in combination with the IDO1-specific inhibitor, NLG919, suppressed tumor progression. Simultaneous administration with both OXA and NLG919 greatly promoted CD8+ T cell infiltration and decreased immunosuppressive cytokine transforming growth factor β (TGF-β) production, whereas increased immunostimulatory cytokines interleukin (IL)-12p70 and interferon (IFN)-γ. We demonstrated the upregulation of IDO1 by OXA, which combined with the IDO1 inhibitor, tremendously potentiated therapeutic effects of OXA against colorectal cancer.

Strategic Incorporation of Polarity in Heme-Displacing Inhibitors of Indoleamine-2,3-dioxygenase-1 (IDO1).

Indoleamine-2,3-dioxygenase-1 (IDO1) has emerged as a target of significant interest to the field of cancer immunotherapy, as the upregulation of IDO1 in certain cancers has been linked to host immune evasion and poor prognosis for patients. In particular, IDO1 inhibition is of interest as a combination therapy with immune checkpoint inhibition. Through an Automated Ligand Identification System (ALIS) screen, a diamide class of compounds was identified as a promising lead for the inhibition of IDO1. While hit 1 possessed attractive cell-based potency, it suffered from a significant right-shift in a whole blood assay, poor solubility, and poor pharmacokinetic properties. Through a physicochemical property-based approach, including a focus on lowering AlogP98 via the strategic introduction of polar substitution, compound 13 was identified bearing a pyridyl oxetane core. Compound 13 demonstrated improved whole blood potency and solubility, and an improved pharmacokinetic profile resulting in a low predicted human dose.

Tumor endothelial cell up-regulation of IDO1 is an immunosuppressive feed-back mechanism that reduces the response to CD40-stimulating immunotherapy

ABSTRACT CD40-stimulating immunotherapy can elicit potent anti-tumor responses by activating dendritic cells and enhancing T-cell priming. Tumor vessels orchestrate T-cell recruitment during immune response, but the effect of CD40-stimulating immunotherapy on tumor endothelial cells has not been evaluated. Here, we have investigated how tumor endothelial cells transcriptionally respond to CD40-stimulating immunotherapy by isolating tumor endothelial cells from agonistic CD40 mAb- or isotype-treated mice bearing B16-F10 melanoma, and performing RNA-sequencing. Gene set enrichment analysis revealed that agonistic CD40 mAb therapy increased interferon (IFN)-related responses in tumor endothelial cells, including up-regulation of the immunosuppressive enzyme Indoleamine 2, 3-Dioxygenase 1 (IDO1). IDO1 was predominantly expressed in endothelial cells within the tumor microenvironment, and its expression in tumor endothelium was positively correlated to T-cell infiltration and to increased intratumoral expression of IFNγ. In vitro, endothelial cells up-regulated IDO1 in response to T-cell-derived IFNγ, but not in response to CD40-stimulation. Combining agonistic CD40 mAb therapy with the IDO1 inhibitor epacadostat delayed tumor growth in B16-F10 melanoma, associated with increased activation of tumor-infiltrating T-cells. Hereby, we show that the tumor endothelial cells up-regulate IDO1 upon CD40-stimulating immunotherapy in response to increased IFNγ-secretion by T-cells, revealing a novel immunosuppressive feedback mechanism whereby tumor vessels limit T-cell activation.

Targeting aerobic glycolysis by dichloroacetate improves Newcastle disease virus-mediated viro-immunotherapy in hepatocellular carcinoma

BackgroundOncolytic viro-immunotherapy holds promise for cancer treatment. While immune activation can be robustly triggered by oncolytic viruses, negative feedback is often upregulated in the tumour microenvironment (TME). Lactate accumulation, signal transducer and activator of transcription 3 (STAT3) activation, indoleamine 2,3-dioxygenase 1 (IDO1) expression, and myeloid-derived suppressor cell (MDSC) infiltration coordinate to shape the immunosuppressive TME.MethodsRepresentative hepatocellular carcinoma (HCC) cell lines and HCC-bearing mice were treated with oncolytic Newcastle disease virus (NDV), alone or in combination with dichloroacetate (DCA, a pyruvate dehydrogenase kinase (PDK) inhibitor).ResultsWe found that infection with oncolytic NDV led to significant induction of the aforementioned suppressive factors. Interestingly, DCA significantly reduced lactate release, STAT3 activation, IDO1 upregulation, and MDSC infiltration in NDV-treated HCC. Consequently, DCA significantly enhanced the antitumour immune responses, leading to improved antitumour efficacy and prolonged survival in mouse models of ascitic and subcutaneous HCC. Furthermore, DCA increased NDV replication in a PDK-1-dependent manner in HCC.ConclusionsTargeting aerobic glycolysis by DCA improves NDV-mediated viro-immunotherapy in HCC by mitigating immune negative feedback and promoting viral replication. These findings provide a rationale for targeting reprogrammed metabolism together with oncolytic virus-mediated viro-immunotherapy for HCC treatment.

Mechanisms of Tolerance Induction through T Regulatory Cells during Chemotherapy-Mediated Immunogenic Cell Death in Acute Myeloid Leukemia

Background: Although the recent advances have allowed the discovery of new and less toxic forms of treatment for acute myeloid leukemia (AML), chemotherapy remains as one of the most used treatments. Some chemotherapeutic agents can induce a type of cell death - immunogenic cell death (ICD) - that can promote modifications in cancer cells, which activates immune system against leukemia cells. Even though this can help the immune system fighting the cancer, chemotherapy is also responsible for inducing tolerogenic mechanisms, that enable cancer cells to escape from immune system control. We previously demonstrated that enzyme indoleamine-2,3-dioxygenase-1 (IDO1) is involved in T regulatory cells (Tregs) induction in AML during ICD induced by chemotherapy. Dying leukemia cells release ATP which binds P2X7 receptor on dendritic cells (DCs), resulting in IDO1 up-regulation. In the same time, ATP can be catabolized by CD39 e CD73 ectonucleotidases expressed on DCs in adenosine with suppressive properties, thus resulting in the stabilization of Tregs phenotype and function. In the present work, we have investigated the role of ATP catabolism in Tregs induction after chemotherapy treatment in AML. Materials and methods: For in vitro experiments,CD14 and CD3 positive cells were obtained from peripheral blood mononuclear cells of healthy donors. HL-60 leukemia cell line cells, untreated or treated with daunorubicin (DNR; 500 ng/ml) or cytarabine (Ara-C; 20 µg/ml) were loaded in immature DCs, previously differentiated from monocytes. After 24 h, immature DCs and DCs matured by treated HL-60 cells or DCs treated with ATP in presence or absence of P2X7 inhibitor, were analyzed for phenotype and used to activate T cells. After 5 days, a detailed phenotype characterization of induced Tregs was performed by flow cytometry. For in vivo experiments, Balbc/J wt mice were subcutaneously injected with 2x106 WEHI-3B leukemia cells. DNR (3 mg/kg), Ara-C (50 mg/kg) or sterile PBS vehicle (placebo) were administered at post inoculum days 7 and 9, then the tumor infiltrating lymphocytes were purified from tumor mass and stained by flow cytometry. Results: Firstly, we in vitro characterized immune phenotype of DCs loaded with HL-60 cells, previously treated with DNR, Ara-C or medium alone. We identified DNR as a potent maturation stimulus as compared to DCs loaded with untreated cells or unloaded immature DCs. In particular, both DNR and Ara-C induced a significant up-regulation of CD83, CD80 and CD86, but only DNR induced a significant up-regulation of CCR7, which is required for DC migration to lymphonodes. Then, the effect of chemotherapy on CD39 and CD73 expression in DCs was also evaluated. DNR induced a significant up-regulation of CD73-the rate limiting step of ATP catabolism, whereas upon Ara-C treatment there was a trend in the up-regulation of both CD39 and CD73. Interestingly, DCs treated with ATP alone achieved similar maturation markers level as DNR, but showed neither CCR7 nor CD39/CD73 up-regulation, which suggests that ATP alone is not sufficient to activate the ATP catabolism pathway. The analysis of Tregs induced after 5 days of co-culture with DCs treated as previously described showed a significant up-regulation of "fitness markers", in particular OX40/CD39 after DNR and OX40/PD-1 after DNR and Ara-C treatment as compared to unloaded immature DCs. Mouse models confirmed the capacity of DNR and Ara-C to induce DCs maturation and activation of ATP catabolism pathways by significantly inducing CD39 and CD73 up-regulation. Moreover, chemotherapy treatment resulted in the stabilization of Tregs suppressive phenotype as demonstrated by the up-regulation of OX40 and ICOS fitness markers in comparison to placebo treatment. Conclusions: Our data suggest that different mechanisms operate in tumor microenvironment. IDO may induce Tregs in an ATP-dependent manner, whereas the ATP catabolism may be involved in the stabilization of Tregs suppressive phenotype. In this context, the specific role of the main bioproduct of ATP catabolism, adenosine, is under investigation. Our results can help to understand the mechanisms of tolerance induction after chemotherapy in AML. Disclosures Cavo: takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; bms: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations, Speakers Bureau; janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; novartis: Honoraria.

IDO1 Maintains Pluripotency of Primed Human Embryonic Stem Cells by Promoting Glycolysis.

Human embryonic stem cells (hESCs) depend on glycolysis for energy supply and pluripotency and switch to oxidative phosphorylation upon differentiation. The underlying mechanisms remain unclear. Here, we demonstrate that indoleamine 2,3-dioxygenase 1 (IDO1) is expressed in primed hESCs and its expression rapidly downregulated upon hESC differentiation. IDO1 is required to maintain pluripotency by suppressing mitochondria activity and promoting glycolysis through the increase of NAD+ /NADH ratio. The upregulation of IDO1 during hESC differentiation suppresses the differentiation of hESCs into certain lineages of cells such as cardiomyocytes, which depend on oxidative phosphorylation to satisfy their high energy demand. Therefore, IDO1 plays important roles in maintaining the pluripotency of hESCs. Stem Cells 2019;37:1158-1165.

High expression of IDO1 and TGF-\u03b21 during recurrence and post infection clearance with Chlamydia trachomatis, are independent of host IFN-\u03b3 response

BackgroundChlamydia trachomatis infections in women continue to be a major public health concern due to their high prevalence and consequent reproductive morbidities. While antibiotics are usually efficient to clear the Chlamydia, repeat infections are common and may contribute to pathological outcomes. Interferon-gamma (IFN-γ)-mediated immunity has been suggested to be protective against reinfection, and represent an important anti-chlamydial agent, primarily via the induction of indoleamine-2,3 dioxygenase 1 (IDO1) enzyme. IDO1 catalyzes the degradation of tryptophan, which can eliminate C. trachomatis infection in vitro. Here, we sought to measure IDO1 expression levels and related immune markers during different C. trachomatis infection statuses (repeated vs single infection vs post antibiotic treatment), in vitro and in vivo.MethodsIn this study, we measured the expression levels of IDO1 and immune regulatory markers, transforming growth factor β1 (TGF-β1) and forkhead box P3 (FoxP3), in vaginal swab samples of C. trachomatis-infected women, with either single or repeated infection. In addition, we used an in vitro co-culture model of endometrial carcinoma cell-line and peripheral blood mononuclear cells (PBMCs) to measure the same immune markers.ResultsWe found that in women with repeated C. trachomatis infections vaginal IDO1 and TGF-β1 expression levels were significantly increased. Whereas, women who cleared their infection post antibiotic treatment, had increased levels of IDO1 and TGF-β1, as well as FoxP3. Similarly, using the in vitro model, we found significant upregulation of IDO1 and TGF-β1 levels in the co-culture infected with C. trachomatis. Furthermore, we found that in PBMCs infected with C. trachomatis there was a significant upregulation in IDO1 levels, which was independent of IFN-γ. In fact, C. trachomatis infection in PBMCs failed to induce IFN-γ levels in comparison to the uninfected culture.ConclusionsOur data provide evidence for a regulatory immune response comprised of IDO1, TGF-β1 and FoxP3 in women post antibiotic treatment. In this study, we demonstrated a significant increase in IDO1 expression levels in response to C. trachomatis infection, both in vivo and in vitro, without elevated IFN-γ levels. This study implicates IDO1 and TGF-β1 as part of the immune response to repeated C. trachomatis infections, independently of IFN-γ.

Abstract A128: Tumor endothelial cells say IDO to CD40-stimulating immunotherapy

Abstract CD40, a tumor necrosis factor receptor superfamily member, is a promising immune-boosting target in cancer immunotherapy due to its role in promoting antitumor responses of immune cells. CD40 is also expressed on endothelial cells but the response of the tumor-associated vasculature to CD40-stimulating immunotherapy has not been studied. Herein, we have performed RNA-sequencing analysis of murine tumor endothelial cells (TECs) isolated from B16.F10 melanoma and MB49 bladder cancer treated with agonistic CD40 monoclonal antibody (mAb) or isotype control. Gene set and gene ontology enrichment analyses of the differentially expressed genes revealed that CD40 mAb treatment induces interferon-γ (IFNγ) signaling in the tumor microenvironment associated with up-regulation of immunosuppressive genes in TECs, including the enzyme indoleamine 2, 3-dioxygenase 1 (IDO1). Importantly, IDO1 was preferentially expressed in endothelial cells in the tumor and was positively correlated to infiltration of T-cells in the tumor microenvironment. In vitro, endothelial cells up-regulated IDO1 in response to T-cell-derived IFNγ, but not in response to CD40-stimulation. Collectively, our data suggest that IDO1 up-regulation in TECs occurs as a response to T-cell activation. Combining CD40 mAb therapy with the IDO1 inhibitor epacadostat delayed tumor growth and increased survival of B16.F10 tumor-bearing mice, which was associated with increased activation of cytotoxic T-cells. Hereby, we have uncovered a novel immunosuppressive feedback mechanism, in which the tumor vasculature limits the response to cancer immunotherapy by up-regulating IDO1. Citation Format: Anna Dimberg, Alexandros Karampatzakis, Sander Tuit, Mohanraj Ramachandran, Grammatiki Fotaki, Luuk van Hooren, Hua Huang, Roberta Lugano, Kaunisto Aura, Peter Ellmark, Sara M Mangsbo, Joachim L. Schultze, Magnus Essand, Maria Georganaki. Tumor endothelial cells say IDO to CD40-stimulating immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A128.

IDO1 expression in glioma molecular subtypes.

e14029Background: Indoleamine 2,3-dioxygenase 1 (IDO1), a tryptophan catabolic enzyme is a key mediator of tumor-induced immunosuppression in multiple tumors. In gliomas, upregulation of IDO1 is as...

Endothelial indoleamine 2,3-dioxygenase-1 regulates the placental vascular tone and is deficient in intrauterine growth restriction and pre-eclampsia

Indoleamine 2,3-dioxygenase-1 (IDO1) mediates the degradation of L-tryptophan (L-Trp) and is constitutively expressed in the chorionic vascular endothelium of the human placenta with highest levels in the microvasculature. Given that endothelial expression of IDO1 has been shown to regulate vascular tone and blood pressure in mice under the condition of systemic inflammation, we asked whether IDO1 is also involved in the regulation of placental blood flow and if yes, whether this function is potentially impaired in intrauterine growth restriction (IUGR) and pre-eclampsia (PE). In the large arteries of the chorionic plate L-Trp induced relaxation only after upregulation of IDO1 using interferon gamma and tumor necrosis factor alpha. However, ex vivo placental perfusion of pre-constricted cotyledonic vasculature with L-Trp decreases the vessel back pressure without prior IDO1 induction. Further to this finding, IDO1 protein expression and activity is reduced in IUGR and PE when compared to gestational age–matched control tissue. These data suggest that L-Trp catabolism plays a role in the regulation of placental vascular tone, a finding which is potentially linked to placental and fetal growth. In this context our data suggest that IDO1 deficiency is related to the pathogenesis of IUGR and PE.

The Clinicopathological and Prognostic Significance of IDO1 Expression in Human Solid Tumors: Evidence from a Systematic Review and Meta-Analysis

Background/Aims: Indoleamine 2,3-dioxygenase 1 (IDO1) is a heme-containing enzyme catalyzing the initial and rate-limiting steps in the kynurenine pathway, which converts tryptophan into kynurenine. Upregulation of IDO1 decreases tryptophan levels and increases the accumulation of kynurenine and its metabolites. These metabolites can affect the proliferation of T cells. Increasing evidence has shown that IDO1 is highly expressed in various cancer types and associated with poor prognosis of cancer patients. However, the results were inconsistent. Methods: We searched the Web of Science, PubMed, Embase and Cochrane library databases to identify studies evaluating the prognostic value of IDO1 in cancer patients. Pooled hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by using fixed-effects/random-effects models. Results: This systematic review and meta-analysis included 2706 patients from 24 articles. The results indicated a shorter overall survival in patients with high expression of IDO1 (hazard ratio [HR] = 2.03, 95% confidence interval [CI]: 1.56-2.63). Furthermore, disease-free survival was worse in patients with high expression of IDO1 (HR = 2.47, 95% CI: 1.46-4.20). Additionally, the pooled odds ratios (ORs) showed that increased IDO1 was significantly associated with tumor differentiation (OR = 1.81, 95% CI: 1.05-3.12), distant metastasis (OR = 1.45, 95% CI: 1.02-2.06), and poor clinical stage (OR = 1.89, 95% CI: 1.13-3.17). However, no significant correlation was observed of increased IDO1 expression with age, sex, lymph node metastasis, and tumor size. Conclusion: High expression of IDO1 is associated with poor clinical outcomes. IDO1 could serve as a biomarker of prognosis and a potential predictive factor of clinicopathology in various cancers. Further studies should be performed to verify the clinical utility of IDO1 in human solid tumors.