Indoleamine 2,3-dioxygenase Protein Research Articles

Indoleamine 2, 3-dioxygenase 1 promoter hypomethylation is associated with poor prognosis in patients with esophageal cancer.

Indoleamine 2, 3‐dioxygenase 1 (IDO1) is a primary enzyme that generates immunosuppressive metabolites. It plays a major role in tumor immunology and is a potential immune‐based therapeutic target. We have reported that IDO1 protein expression was associated with an unfavorable clinical outcome in esophageal cancer. Recently, it has been reported that IDO1 expression is regulated by methylation of the IDO1 promoter. Thus, the aim of this study was to examine the relationship between IDO1 expression, IDO1 promoter methylation, and clinicopathological features in esophageal cancer. We first confirmed changes in IDO1 expression levels in vitro by treating cells with 5‐azacytidine. We then evaluated the relationship between IDO1 expression levels, IDO1 promoter methylation (bisulfite pyrosequencing), and clinicopathological features using 40 frozen samples and 242 formalin‐fixed, paraffin‐embedded samples resected from esophageal cancer patients. We treated cell lines with 5‐azacytidine, and the resulting hypomethylation induced significantly higher IDO1 expression (P < .001). In frozen samples, IDO1 expression levels correlated inversely with IDO1 promoter methylation levels (R = −0.47, P = .0019). Furthermore, patients in the IDO1 promoter hypomethylation group (n = 67) had a poor prognosis compared with those in the IDO1 promoter hypermethylation group (n = 175) (overall survival, P = .011). Our results showed that IDO1 promoter hypomethylation regulated IDO1 expression and was associated with a poor prognosis in esophageal cancer patients.

Shikonin Prolongs Allograft Survival via Induction of CD4+FoxP3+ Regulatory T Cells.

A transplanted organ is usually rejected without any major immunosuppressive treatment because of vigorous alloimmune responsiveness. However, continuous global immunosuppression may cause severe side effects, including nephrotoxicity, tumors, and infections. Therefore, it is necessary to seek novel immunosuppressive agents, especially natural ingredients that may provide sufficient efficacy in immunosuppression with minimal side effects. Shikonin is a bioactive naphthoquinone pigment, an ingredient originally extracted from the root of Lithospermum erythrorhizon. Previous studies have shown that shikonin regulates immunity and exerts anti-inflammatory effects. In particular, it can ameliorate arthritis in animal models. However, it is unclear whether shikonin inhibits alloimmunity or allograft rejection. In this study and for the first time, we demonstrated that shikonin significantly prolonged the survival of skin allografts in wild-type mice. Shikonin increased the frequencies of CD4+Foxp3+ regulatory T cells (Tregs) post-transplantation and induced CD4+Foxp3+ Tregs in vitro as well. Importantly, depleting the Tregs abrogated the extension of skin allograft survival induced by shikonin. It also decreased the frequencies of CD8+CD44highCD62Llow effector T cells and CD11c+CD80+/CD11c+CD86+ mature DCs after transplantation. Moreover, we found that shikonin inhibited the proliferation of T cells in vitro and suppressed their mTOR signaling. It also reduced the gene expression of pro-inflammatory cytokines, including IFNγ, IL-6, TNFα, and IL-17A, while increasing the gene expression of anti-inflammatory mediators IL-10, TGF-β1, and indoleamine-2, 3-dioxygenase (IDO) in skin allografts. Further, shikonin downregulated IDO protein expression in skin allografts and DCs in vitro. Taken together, shikonin inhibits allograft rejection via upregulating CD4+Foxp3+ Tregs. Thus, shikonin is a novel immunosuppressant that could be potentially used in clinical transplantation.

Rational design, synthesis and biological evaluation of ubiquinone derivatives as IDO1 inhibitors

Indoleamine 2,3-dioxygenase 1 (IDO1) is an attractive therapeutic target for the treatment of cancer, chronic viral infections and neurological disorders characterized by pathological immune stimulation. Herein, a series of known metal-chelating ubiquinone derivatives were designed, synthesized and evaluated for the IDO1 inhibiting activities. The docking studies showed that the compounds 11, 16, 18 and coenzyme-Q1 exhibited different binding modes to IDO1 protein. Among these compounds, the most active compound is 16d with an IC50 of 0.13 μM in enzymatic assay. The results reveal that a possible halogen bonding interaction between the bromine atom (3-Br) and Cys129 significantly enhances the inhibition activity against IDO1. This study provides structural insights of the interactions between ubiquinone analogues and IDO1 protein for the further modification and optimization.

Reliable detection of indoleamine 2,3 dioxygenase-1 in murine cells and tissues.

The essential amino acid tryptophan is catabolized by the first and rate-limiting enzyme of the kynurenine pathway, indoleamine 2,3-dioxygenase-1 (IDO1). IDO1 is implicated in several diseases including cancer, chronic infection, autoimmune disorders and neurodegenerative diseases. Antibodies that accurately recognize human IDO1 protein in situ in tissues are available, including clone 10.1 generated in our laboratory and now widely available through commercial sources (Muller, DuHadaway, Sutanto-Ward, Donover, & Prendergast, 2005). However, until recently, there were no antibodies available to accurately detect murine IDO1 protein in situ in preclinical mouse models of disease. Such probes are crucial to establish cellular mechanisms since IDO1 appears to act in different cell types depending on disease context, but reliable probes have been elusive in the field. Recently we addressed this issue with the development of IDO1 monoclonal antibody 4B7, the specificity of which was fully validated by a lack of binding to tissues derived from mice that are genetically deficient in IDO1. This antibody offers a reagent that is unique in the field for specifically recognizing the enzyme in murine tissues, addressing the acute need for a reliable tool to conduct immunohistology in preclinical disease models.

Indoleamine 2,3-dioxygenase expression and overall survival in patients diagnosed with breast cancer in Pakistan.

BackgroundImmune dysfunction in breast cancer patients is well established. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme that is linked with progression of cancer. IDO is overexpressed in triple-negative breast cancer (TNBC) cases.Materials and methodsWe conducted the first study to analyze IDO expression and overall survival in breast cancer cases in Pakistan. Expression of IDO, estrogen receptor (ER), progesterone receptor (PR), and human EGF receptor 2 (HER2) was evaluated by immunohistochemistry. Formalin-fixed paraffin-embedded breast cancer tissues of 100 (TNBC, n=49 and non-TNBC, n=51) patients were obtained from Shaukat Khanum Memorial Cancer Hospital and Research Centre. IDO expression was analyzed in association with clinicopathological features and overall survival. A total of 100 patients were classified based on the ordinal IDO score variables as low, medium, and high. In addition, overall mean age and SD of patients was 48.28±11.82.ResultsImmunohistochemical analysis showed that high IDO was observed in the TNBC patients (65.3%) compared to that in the non-TNBC patients (33.3%). Multivariable analyses showed that TNBC was an independent risk factor for high IDO expression. Overall survival was also significantly associated with IDO score.ConclusionOur study showed that IDO protein expression is higher in TNBC patients (P<0.01) and may suggest its role in disease pathogenesis. TNBC might be effectively treated with IDO inhibitors. Furthermore, high IDO expression is considerably associated with overall decreased patient survival. IDO might be utilized as a potential biomarker and immunotherapeutic target in breast cancer patients.

Identification of a 2-propanol analogue modulating the non-enzymatic function of indoleamine 2,3-dioxygenase 1

Indoleamine 2,3 dioxygenase 1 (IDO1) is a metabolic enzyme that catalyzes the conversion of the essential amino acid tryptophan (Trp) into a series of immunoactive catabolites, collectively known as kynurenines. Through the depletion of Trp and the generation of kynurenines, IDO1 represents a key regulator of the immune responses involved in physiologic homeostasis as well as in neoplastic and autoimmune pathologies. The IDO1 enzyme has been described as an important immune checkpoint to be targeted by catalytic inhibitors in the treatment of cancer. In contrast, a defective expression/activity of the enzyme has been demonstrated in autoimmune diseases. Beside its catalytic activity, the IDO1 protein is endowed with an additional function associated with the presence of two immunoreceptor tyrosine-based inhibitory motifs (ITIMs), which, once phosphorylated, bind SHP phosphatases and mediate a long-term immunoregulatory activity of IDO1. Herein, we report the screening of a focused library of molecules bearing a propanol core by a protocol combining microscale thermophoresis (MST) analysis and a cellular assay. As a result, the combined screening identified a 2-propanolol analogue, VIS351, as the first potent activator of the ITIM-mediated function of the IDO1 enzyme. VIS351 displayed a good dissociation constant (Kd = 1.90 μM) for IDO1 and a moderate cellular inhibitor activity (IC50 = 11.463 μM), although it did not show any catalytic inhibition of the recombinant IDO1 enzyme. Because we previously demonstrated that the enzymatic and non-enzymatic (i.e., ITIM-mediated) functions of IDO1 reside in different conformations of the protein, we hypothesized that in the cellular system VIS351 may shift the dynamic conformational balance towards the ITIM-favoring folding of IDO1, resulting in the activation of the signaling rather than catalytic activity of IDO1. We demonstrated that VIS351 activated the ITIM-mediated signaling of IDO1 also in mouse plasmacytoid dendritic cells, conferring those cells an immunosuppressive phenotype detectable in vivo. Thus the manuscript describes for the first time a small molecule as a positive modulator of IDO1 signaling function, paving the basis for an innovative approach to develop first-in-class drugs acting on the IDO1 target.

Abstract LB-285: Non-enzyme IDO1 activity and its immunosuppressive effects in glioblastoma

Abstract Purpose: Adult glioblastoma (GBM) is the most common primary malignant brain tumor of the central nervous system (CNS) with a median patient survival of 15-20 months. A consistent feature of GBM is the presence of indoleamine 2,3 dioxygenase 1 (IDO1) expressed by tumor cells. IDO1 is canonically characterized as an enzyme that metabolizes tryptophan (Trp) into kynurenines (Kyns). Tryptophan metabolism is the primary feature associated with IDO1-mediated immune suppression - primarily derived from in vitro study. Less appreciated is the recent find that, plasmacytoid dendritic cells (pDCs) utilize IDO1 to activate the non-canonical NFκB pathway, independent of Trp metabolism, resulting in greater levels of immunosuppression. The scientific premise of our study was therefore to determine whether GBM cell IDO1 is capable of mediating immunosuppression without associated enzyme activity. Experimental methods: IDO1-deficient (IDO1-/-) glioma cells isolated from mice that spontaneously develop GBM [GFAP(ERT2)→Cre+/-;pTENfl/fl;Rbfl/fl;p53fl/fl;IDO1-/-] were transduced with lentiviral particles expressing wild-type or modified mouse IDO1 cDNA fused to a mGFP tag. Stably expressing cells were enriched for high IDO1/GFP expression by fluorescence-activated cell sorting and confirmed with RT-PCR and Western blotting. The effects of IDO1 modification on Trp/Kyn was quantified by HPLC. IDO1-/- syngeneic mice were intracranially-engrafted with modified GBM cells and studied for regulatory T cell (Treg; CD4+CD25+FoxP3+)/MDSC accumulation. Results: (i) Viral transduction yielded stable expression of murine IDO1 mRNA and protein; (ii) the mGFP tag did not interfere with IDO1 enzyme activity in unmodified GBM cells; (iii) the histidine 350 to alanine (H350A), as well as aspartic acid 278 to alanine (D278A) mutations cause decreased or ablated IDO1 enzyme activity, respectively; (iv) ITIM mutation of tyrosine into glutamate (YE), as well as tyrosine into phenylalanine (YF), had a minimal effect on IDO1 enzyme activity. Conclusions: We established new, novel, GFP-tagged mouse GBM cell lines to dissect the immunosuppressive contributions of Trp metabolism vs. non-enzyme functions as mediated by IDO1. Some GBM cell lines expressed high IDO1 with no Trp catabolic activity. GBM with IDO1-associated ITIM mutations showed marginal effects on enzyme activity. The analysis of in vitro GBM cell growth/cell death rate, invasion, and effects on co-cultured Tregs, as well as the in vivo analysis of GBM-infiltrating Treg/MDSC levels and impact on overall survival, will be presented. Citation Format: Lijie Zhai, Jun Qian, Erik Ladomersky, Alicia Lenzen, Kristen L. Lauing, Derek A. Wainwright. Non-enzyme IDO1 activity and its immunosuppressive effects in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-285.

Feiji Recipe inhibits the growth of lung cancer by modulating T-cell immunity through indoleamine-2,3-dioxygenase pathway in an orthotopic implantation model

ObjectiveEscape from the body’s immune response is a basic characteristic of lung cancer, and indoleamine-2,3-dioxygenase (IDO) plays a key role in mediating immune escape of non-small-cell lung cancer, which leads to recurrence and metastasis. Feiji Recipe, a compound Chinese herbal medicine, has the effect of stabilizing lesions and prolonging survival in patients with lung cancer. The purpose of this study was to investigate the mechanisms underlying the anticancer properties of Feiji Recipe. MethodsAn orthotopic transplant model of mouse Lewis lung cancer, with stable expression of IDO gene, was established in C57BL/6 mice. Optical imaging was used to observe the effects of Feiji Recipe in the treatment of lung cancer in vivo. The effects of Feiji Recipe on the proliferation of mouse Lewis lung cancer cell line 2LL, 2LL-enhanced green fluorescent protein (2LL-EGFP) and 2LL-EGFP-IDO were investigated, and the apoptosis of T-cells was examined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide using flow cytometry. Chemical composition of Feiji Recipe was validated by high-performance liquid chromatography. ResultsCompared to the control group, the survival of animals treated with Feiji Recipe was significantly prolonged (P = 0.0074), and the IDO protein level decreased (P = 0.0072); moreover, the percentages of CD4+CD25+ T-cells and Foxp3+ T-cells were significantly decreased (P < 0.05). The molecular mechanism of Feiji Recipe against lung cancer may relate to the regulation of immune cells, such as T-cells and regulatory T-cells. ConclusionThe molecular mechanism of Feiji Recipe in treatment of lung cancer is to restore the function of T-cells in the cancer microenvironment through interfering with the IDO pathway.

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.

PCC0208009 enhances the anti-tumor effects of temozolomide through direct inhibition and transcriptional regulation of indoleamine 2,3-dioxygenase in glioma models.

Indoleamine 2,3-dioxygenase (IDO), which is highly expressed in human glioblastoma and involved in tumor immune escape and resistance to chemotherapy, is clinically correlated with tumor progression and poor clinical outcomes, and is a promising therapeutic target for glioblastoma. IDO inhibitors are marginally efficacious as single-agents; therefore, combination with other therapies holds promise for cancer therapy. The aim of this study was to investigate the anti-tumor effects and mechanisms of the IDO inhibitor PCC0208009 in combination with temozolomide. The effects of PCC0208009 on IDO activity inhibition, and mRNA and protein expression in HeLa cells were observed. In the mouse glioma GL261 heterotopic model, the effects of PCC0208009 on l-kynurenine/tryptophan (Kyn/Trp), tumor growth, flow cytometry for T cells within tumors, and immunohistochemistry for IDO and Ki67 were examined. In the rat glioma C6 orthotopic model, animal survival, flow cytometry for T cells within tumors, and immunohistochemistry for proliferating cell nuclear antigen (PCNA) and IDO were examined. The results show that PCC0208009 is a highly effective IDO inhibitor, not only directly inhibiting IDO activity but also participating in the gene regulation of IDO expression at the transcription and translation levels. PCC0208009 significantly enhanced the anti-tumor effects of temozolomide in GL261 and C6 models, by increasing the percentages of CD3+, CD4+, and CD8+ T cells within tumors and suppressing tumor proliferation. These findings indicate that PCC0208009 can potentiate the anti-tumor efficacy of temozolomide and suggest that combination of IDO inhibitor-based immunotherapy with chemotherapy is a potential strategy for brain tumor treatment.

Effects of Xiao Yao San on interferon-α-induced depression in mice

Background and objectiveXiao Yao San (XYS) is a traditional Chinese medicine used to treat depression; however, the mechanism underlying its antidepressant properties remains unclear. The objective of the present study was to investigate the effects and action mechanisms of XYS on interferon-α-induced depression in mice. MethodMice were divided into six groups: control; model; low-, medium-, and high-dose XYS; and escitalopram-treated group. Except for the control mice, all groups of mice were injected with interferon (IFN)-α to establish the depression model. XYS and escitalopram were then administered to the respective mice daily for 21 days. Sucrose preference test (SPT), forced swim test (FST), and tail suspension test (TST) were used to measure behavioral indices. High-performance liquid chromatography (HPLC) was used to measure serotonin (5-HT) concentrations, while western blots were used to examine indoleamine-2,3-dioxygenase 1 (IDO1) expression in the dorsal raphe nucleus (DRN). The number of microglia in the DRN was observed using immunofluorescence. ResultsCompared with that of the control group, the model group showed a significant decrease in sucrose consumption (P < 0.05) and significant increase in the duration of immobility in the FST and TST (P < 0.05). These parameters improved significantly after XYS or escitalopram treatment. There was also a significantly higher and lower expression of IDO1 protein and 5-HT in the mouse DRN, respectively, which were reversed by administering XYS and escitalopram (P < 0.05). Moreover, the number of microglia in the mouse DRN increased significantly and was reduced by XYS and escitalopram (P < 0.05). ConclusionXYS reduced the number of microglia and expression of IDO1, which increased the levels of 5-HT in the mouse DRN and, thereby, improved the depressive behavior of mice. This may explain, at least in part, the antidepressant properties of XYS in patients.

A novel immunohistochemical score to predict early mortality in acute myeloid leukemia patients based on indoleamine 2,3 dioxygenase expression

Indoleamine 2,3 dioxygenase-1 (IDO-1) is an enzyme in the kynurenine pathway which augments tumor-induced immune tolerance. Previous studies in childhood acute myeloid leukemia (AML) have shown a negative correlation of IDO-1 mRNA expression with outcomes. The aim of our study was to develop a practical and objective immunohistochemical technique to quantify IDO-1 expression on diagnostic bone marrow biopsies of AML patients in order to facilitate its use in routine clinical practice. IDO-1 mRNA was extracted from diagnostic bone marrow specimens from 29 AML patients. IDO-1 protein expression was assessed in 40 cases via immunohistochemistry and quantified by a novel ‘composite IDO-1 score’. In a univariate analysis, higher age (p = 0.0018), male gender (p = 0.019), high risk cytogenetics (p = 0.002), higher IDO-1 mRNA (p = 0.005), higher composite IDO-1 score (p < 0.0001) and not undergoing allogeneic stem cell transplant (SCT, p = 0.0005) predicted poor overall survival. In a multivariate model that included the aforementioned variables, higher composite IDO-1 score (p = 0.007) and not undergoing allogeneic SCT (p = 0.007) was found to significantly predict poor outcomes. Further, patients who failed induction had higher composite IDO-1 score (p = 0.01). In conclusion, ‘composite IDO-1 score’ is a prognostic tool that can help identify a certain subset of AML patients with ‘early mortality’. This unique subset of patients can potentially benefit from specific IDO-1 inhibitor therapy, currently in clinical trials.

Response of human periodontal ligament stem cells to IFN-\u03b3 and TLR-agonists

Periodontal ligament stem cells similarly to the mesenchymal stem cells of other tissues possess immunomodulatory properties, which are regulated by different cytokines, particularly by interferon-γ (IFN-γ). In contrast, less information is provided about the effect of toll-like receptors ligand on immunomodulatory properties of these cells. In the present study we investigated the response of human periodontal ligament stem cells (hPDLSCs) in response to simultaneous stimulation with IFN-γ and toll-like receptor (TLR) agonists. The resulting expression of indoleamine-2,3-dioxygenase-1 (IDO-1), interleukin (IL)-6, IL-8 and monocyte chemotactic protein 1 (MCP-1) was investigated. The expression of IDO-1 was upregulated by IFN-γ in both gene and protein levels. TLR2 agonists Pam3CSK4 induced gene expression of IDO-1, but had no effect on protein expression. IFN-γ induced IDO-1 protein expression was further enhanced by Pam3CSK4. TLR-4 agonist E. coli LPS has no significant effect on neither basal nor IFN-γ induced IDO-1 protein expression. The production of IL-6, IL-8, and MCP-1 was induced by TLR agonists. Neither basal nor TLR agonists induced production of these proteins was affected by IFN-γ. Our data shows potential interaction between IFN-γ and TLR2 responses in hPDLSCs, which might be involved in regulation of immune response in inflammatory diseases, and particularly periodontitis.

Discovery of imidazoleisoindole derivatives as potent IDO1 inhibitors: Design, synthesis, biological evaluation and computational studies

Indoleamine-2,3-dioxygenase-1 (IDO1) is an attractive target for cancer immunotherapy. Herein, a series of novel imidazoleisoindole derivatives were prepared and evaluated for their ability to inhibit IDO1. Among these, derivative 11r was the most active compound with nanomolar potency in the Hela cell-based assay, while showed negligible cellular toxicity. UV-visible spectra study demonstrated that compounds 11p and 11r bound to IDO1 and coordinated with the heme iron. Furthermore, they could significantly promote T cell proliferation, increase IFN-γ production, and reduce the numbers of Foxp3+ regulatory T cells. Finally, induced fit docking (IFD) and quantum mechanics/molecular mechanics (QM/MM) calculation were performed to understand the interactions of these compounds to IDO1 protein, which provided a comprehensive guide for further structural modification and optimization.

Indoleamine 2,3-Dioxygenase 1, Increased in Human Gastric Pre-Neoplasia, Promotes Inflammation and Metaplasia in Mice and Is Associated With Type II Hypersensitivity/Autoimmunity

Chronic gastrointestinal inflammation increases the risk of cancer by mechanisms that are not well understood. Indoleamine-2,3-dioxygenase 1 (IDO1) is a heme-binding enzyme that regulates the immune response via catabolization and regulation of tryptophan availability for immune cell uptake. IDO1 expression is increased during the transition from chronic inflammation to gastric metaplasia. We investigated whether IDO1 contributes to the inflammatory response that mediates loss of parietal cells leading to metaplasia. Chronic gastric inflammation was induced in Ido1-/- and CB57BL/6 (control) mice by gavage with Helicobacter felis or overexpression of interferon gamma in gastric parietal cells. We also performed studies in Jh-/- mice, which are devoid of B cells. Gastric tissues were collected and analyzed by flow cytometry, immunostaining, and real-time quantitative polymerase chain reaction. Plasma samples were analyzed by enzyme-linked immunosorbent assay. Gastric tissues were obtained from 20 patients with gastric metaplasia and 20 patients without gastric metaplasia (controls) and analyzed by real-time quantitative polymerase chain reaction; gastric tissue arrays were analyzed by immunohistochemistry. We collected genetic information on gastric cancers from The Cancer Genome Atlas database. H felis gavage induced significantly lower levels of pseudopyloric metaplasia in Ido1-/- mice, which had lower frequencies of gastric B cells, than in control mice. Blood plasma from H felis-infected control mice had increased levels of autoantibodies against parietal cells, compared to uninfected control mice, but this increase was lower in Ido1-/- mice. Chronically inflamed stomachs of Ido1-/- mice had significantly lower frequencies of natural killer cells in contact with parietal cells, compared with stomachs of control mice. Jh-/- mice had lower levels of pseudopyloric metaplasia than control mice in response to H felis infection. Human gastric pre-neoplasia and carcinoma specimens had increased levels of IDO1 messenger RNA compared with control gastric tissues, and IDO1 protein colocalized with B cells. Co-clustering of IDO1 messenger RNA with B-cell markers was corroborated by The Cancer Genome Atlas database. IDO1 mediates gastric metaplasia by regulating the B-cell compartment. This process appears to be associated with type II hypersensitivity/autoimmunity. The role of autoimmunity in the progression of pseudopyloric metaplasia warrants further investigation.

Abstract 5581: Development of 2nd generation indoleamine 2,3-dioxygenase 1 (IDO1) selective inhibitors

Abstract Harnessing the immune system via immune checkpoint blockade (e.g. anti PD-1, anti PD-L1, anti CTLA4) has led to fast and long lived responses in cancer patients. Response rates however are low and new treatments that enhance these rates are needed. Recent studies have shown that the administration of immune checkpoint blockers is associated with the overexpression of indoleamine 2,3-dioxygenase 1 (IDO1). The resulting immunoregulatory phenotype counteracts immune checkpoint blockade and allows for cancer progression. The discovery of IDO1 inhibitors, and the potential to combine them with immune checkpoint blockers, therefore represents an attractive strategy to fight cancer. We carried out a ligand-based virtual screen with &amp;gt; 1,000,000 commercially available small molecules. In vitro screening of the resulting 610 virtual hits provided us with 2 IDO1-selective, 2 TDO2-selective and 2 IDO1/TDO2-dual confirmed hits. (TDO2 is a protein with similar biochemical activity to IDO1 that is essential to tryptophan homeostasis.) A subsequent Hit to Lead campaign led to the identification of novel chemotypes that display potency similar or superior to IDO1 inhibitors currently under clinical investigation in IFN-γ stimulated (i.e. IDO1+) HeLa cells, with no sign of cytotoxicity. We have demonstrated that these compounds are &amp;gt; 1000-fold selective for IDO1 over TDO2 using cellular assays. IDO1 upregulation by cancer cells is known to be one of the mechanisms by which cancer cells evade the immune system. In an in vitro co-culture assay of cancer cells and T cells we have demonstrated our compounds can rescue T cell proliferation with EC50 values between 10 and 50 nM. We have also demonstrated that our compounds inhibit IDO1 in monocyte derived human dendritic cells. Interestingly, despite this potent cellular activity demonstrated in multiple disease relevant cellular assays, this chemotype failed to inhibit recombinant IDO1 in an isolated biochemical assay performed under reducing conditions, whereas the reference compound epacadostat provided activity comparable to literature values. In order to confirm our cellular effects were due to direct inhibition of IDO1 we set up thermal shift assays. Thermal shift assays using purified IDO1 protein have demonstrated that our compounds directly bind IDO1, and cellular thermal shift assays have confirmed direct target engagement in intact cells (stimulated for IDO1 expression). These compounds have physicochemical properties that would support oral dosing and display low in vitro CYP450 and hERG inhibition, thus reducing the risk of toxicity in the clinic. Our IDO1 inhibitors show a novel differentiated mode of action at the cellular level, and the consequences of this profile in terms of in vivo characterisation is ongoing. Citation Format: Thomas Pesnot, Sachin Mahale, Philip MacFaul, John Maclean, Caroline Phillips, Matilda Bingham, Catherine Eagle, James Kelly, Abhijith Thippeswamy, Simon Armitage, Aleksandr Grisin, Sheenagh Aiken, Lucy Cartwright, Richard Armer. Development of 2nd generation indoleamine 2,3-dioxygenase 1 (IDO1) selective inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5581. doi:10.1158/1538-7445.AM2017-5581

Identification and preliminary structure–activity relationships of 1-Indanone derivatives as novel indoleamine-2,3-dioxygenase 1 (IDO1) inhibitors

Indoleamine 2,3-dioxygenase 1 (IDO1) plays a vital role in the catabolism of tryptophan along with the kynurenine pathway which is involved in many human diseases including cancer, Alzheimer’s disease, etc. In this study, compound 1 bearing a 1-Indanone scaffold was identified as a novel IDO1 inhibitor by structure-based virtual screening, with moderate to good enzymatic and cellular inhibitory activities. Also, surface plasmon resonance analysis validated the direct interaction between compound 1 and IDO1 protein. The preliminary SAR was further explored and the binding mode with IDO1 protein was predicted by experiment along with molecular docking. Subsequent ADME properties of these active compounds were analyzed in silico, and the results showed good pharmacokinetic efficiencies. We believe this study contributes a lot to the structural diversity for the future development of highly potent IDO1 inhibitors.

Structural insights into the binding mechanism of IDO1 with hydroxylamidine based inhibitor INCB14943

IDO1 (indoleamine 2, 3-dioxygenase 1), a well characterized immunosuppressive enzyme, has attracted growing attention as a potential target for cancer immunotherapy. Hydroxylamidine compounds INCB024360 and INCB14943 (INCB024360 analogue) are highly effective IDO1 inhibitors. INCB024360 is undergoing clinical trials for treatment of various types of human cancer. Here, we determined the co-crystal structure of IDO1 and INCB14943, and elucidate the detailed binding mode. INCB14943 binds to heme iron in IDO1 protein through the oxime nitrogen. Further analysis also reveals that a halogen bonding interaction between the chlorine atom (3-Cl) of INCB14943 and the sulphur atom of C129 significantly improves the inhibition activity against IDO1. Comparing with the other reported inhibitors, the oxime nitrogen and halogen bond interaction are identified as the unique features of INCB14943 among the IDO1 inhibitors. Thus, our study provides novel insights into the interaction between a small molecule inhibitor INCB14943 and IDO1 protein. The structural information will facilitate future IDO1 inhibitor design.

The Proteasome Inhibitor Bortezomib Controls Indoleamine 2,3-Dioxygenase 1 Breakdown and Restores Immune Regulation in Autoimmune Diabetes.

Bortezomib (BTZ) is a first-in-class proteasome inhibitor approved for the therapy of multiple myeloma that also displays unique regulatory activities on immune cells. The enzyme indoleamine 2,3-dioxygenase 1 (IDO1) is a tryptophan metabolizing enzyme exerting potent immunoregulatory effects when expressed in dendritic cells (DCs), the most potent antigen-presenting cells capable of promoting either immunity or tolerance. We previously demonstrated that, in inflammatory conditions, IDO1 is subjected to proteasomal degradation in DCs, turning these cells from immunoregulatory to immunostimulatory. In non-obese diabetic (NOD) mice, an experimental model of autoimmune diabetes, we also identified an IDO1 defect such that the DCs do not develop tolerance toward pancreatic islet autoantigens. We found that BTZ rescues IDO1 protein expression in vitro in a particular subset of DCs, i.e., plasmacytoid DCs (pDCs) from NOD mice. When administered in vivo to prediabetic mice, the drug prevented diabetes onset through IDO1- and pDC-dependent mechanisms. Although the drug showed no therapeutic activity when administered alone to overtly diabetic mice, its combination with otherwise suboptimal dosages of autoimmune-preventive anti-CD3 antibody resulted in disease reversal in 70% diabetic mice, a therapeutic effect similar to that afforded by full-dosage anti-CD3. Thus, our data indicate a potential for BTZ in the immunotherapy of autoimmune diabetes and further underline the importance of IDO1-mediated immune regulation in such disease.

Brief Report: Proteasomal Indoleamine 2,3-Dioxygenase Degradation Reduces the Immunosuppressive Potential of Clinical Grade-Mesenchymal Stromal Cells Undergoing Replicative Senescence.

Owing to their immunosuppressive properties, mesenchymal stromal cells (MSCs) obtained from bone marrow (BM-MSCs) or adipose tissue (ASCs) are considered a promising tool for cell therapy. However, important issues should be considered to ensure the reproducible production of efficient and safe clinical-grade MSCs. In particular, high expansion rate, associated with progressive senescence, was recently proposed as one of the parameters that could alter MSC functionality. In this study, we directly address the consequences of replicative senescence on BM-MSC and ASC immunomodulatory properties. We demonstrate that MSCs produced according to GMP procedures inhibit less efficiently T-cell, but not Natural Killer (NK)- and B-cell, proliferation after reaching senescence. Senescence-related loss-of-function is associated with a decreased indoleamine 2,3-dioxygenase (IDO) activity in response to inflammatory stimuli. In particular, although STAT-1-dependent IDO expression is transcriptionally induced at a similar level in senescent and nonsenescent MSCs, IDO protein is specifically degraded by the proteasome in senescent ASCs and BM-MSCs, a process that could be reversed by the MG132 proteasome inhibitor. These data encourage the use of appropriate quality controls focusing on immunosuppressive mechanisms before translating clinical-grade MSCs in the clinic. Stem Cells 2017;35:1431-1436.