Indoleamine 2,3-dioxygenase Expression Research Articles

IDO1 Promotes the Progression of NSCLC by Regulating the Polarization of M2 Macrophages.

Non-small cell lung cancer (NSCLC) is currently a problem in the clinic and in society. Tumor-related macrophages (TAMs) in the tumor microenvironment (TME) play a vital role in the development of NSCLC. Bioinformatics was used to analyze the role of Indoleamine 2,3-dioxygenase 1 (IDO1) in NSCLC and the correlation of its expression with CD163 expression. The expression of CD163 and IDO1 was measured by immunohistochemistry, and their colocalization was assessed by immunofluorescence. M2 macrophage polarization was induced, and a coculture model of NSCLC cells and macrophages was established. Bioinformatics analysis showed that IDO1 promoted the metastasis and differentiation of NSCLC and inhibited DNA repair. Moreover, the expression of IDO1 was positively correlated with CD163 expression. We discovered that IDO1 expression was related to M2 macrophage differentiation. In vitro, we showed that increased IDO1 expression promoted the invasion, proliferation, and metastasis of NSCLC cells. In conclusion, we determined that IDO1 can regulate the M2 polarization of TAMs and promote the progression of NSCLC, which provides partial theoretical evidence for the use of IDO1 inhibitors in the treatment of NSCLC.

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.

IDO1 Protein Is Expressed in Diagnostic Biopsies from Both Follicular and Transformed Follicular Patients.

Follicular lymphoma (FL) is a lymphoid neoplasia characterized by an indolent clinical nature. Despite generally favorable prognoses, early progression and histological transformation (HT) to a more aggressive lymphoma histology remain the leading causes of death among FL patients. To provide a basis for possible novel treatment options, we set out to evaluate the expression levels of indoleamine 2,3-dioxygenase 1 (IDO1), an immunoinhibitory checkpoint molecule, in follicular and transformed follicular biopsies. The expression levels of IDO1 were assessed using immunohistochemical staining and digital image analysis in lymphoma biopsies from 33 FL patients without subsequent HT (non-transforming FL, nt-FL) and 20 patients with subsequent HT (subsequently transforming FL, st-FL) as well as in paired high-grade biopsies from the time of HT (transformed FL, tFL). Despite no statistical difference in IDO1 expression levels seen between the groups, all diagnostic and transformed lymphomas exhibited positive expression, indicating its possible role in novel treatment regimens. In addition, IDO1 expression revealed a positive correlation with another immune checkpoint inhibitor, namely programmed death 1 (PD-1). In summary, we report IDO1 expression in all cases of FL and tFL, which provides the grounds for future investigations of anti-IDO1 therapy as a possible treatment for FL patients.

Abstract 4341: Indoleamine 2,3-dioxygenase 1 is highly expressed in tertiary lymphoid structures and associated with improved outcome in patients with advanced non-small cell lung cancer treated with anti-PD1/PDL1 inhibitors

Abstract Background: Immune checkpoint inhibitors (ICI) has revolutionized the management of patients with non-small cell lung cancer (NSCLC). However, most patients with advanced NSCLC patients displayed primary resistance to ICI. Indoleamine 2,3-dioxygenase 1 (IDO1) may play a role in primary resistance by catabolizing tryptophan to several immunosuppressive metabolites such as kynurenine. The aim of our study was to investigate the role of IDO1 expression in the outcome of NSCLC patients treated with immunotherapy. Methods: We analyzed the largest NSCLC gene expression (GE) dataset worldwide including 891 pre-treatment tumors from POPLAR and OAK studies, two RCT assessing the efficacy of atezolizumab vs docetaxel in NSCLC. We then confirm our findings with multiplex immunofluorescence (mIF) and digital pathology analysis to investigate the correlation between expression of IDO1 by tumor cells and spatial distribution of CD8+ T cells. Results: The PFS of IDO1high patients was significantly higher than IDO1low (3.81 vs 1.89months, p=7.13e-09). Strikingly, high IDO1 expression was also associated with better ORR (19.9% vs 5.2%, p=9.93e-05) and improved OS (15.9 vs 9.65 months, p=6.35e-06). When adjusting for covariates (histological subtype, TLS signature, PD-L1 expression), IDO1 remained independently associated with PFS (HR 1.54, p=4.1e-4) and OS (HR 1.43, p=8.2e-3). None of these correlations were observed in the docetaxel arm, suggesting a predictive value of IDO1 GE specifically for response to atezolizumab. Using a deconvolution approach, the tumor microenvironment composition differed significantly between IDO1high and IDO1low tumors. Indeed, IDO1high tumors were characterized by the highest expression of genes specific to immune populations such as interferon-gamma-producing T helper 1 (Th1) cells, CD8+ T cells, natural killer cells, cytotoxic lymphocytes, and B cells. To further validate our findings, we performed mIF on 53 NSCLC tumors. Overall, elevated IDO1 expression by tumor cells was correlated with increased CD8+/PD1+ T cells infiltration (p=0.001). Spatial cell distribution analysis also revealed that the relative distance between tumor cells and CD8+ T cells was significantly lower in IDO1high compared to IDO1low patients. Interestingly, 52% of tumors were characterized by the presence of TLS and IDO1 was observed in most TLS analyzed. Conclusions: IDO1 expression by tumor cells in NSCLC is associated with improved outcome in patients with NSCLC, independently of PDL1 expression score. IDO1 overexpression in NSCLC is associated with increased immune activity and may represent a negative feedback mechanism to CD8+ T cell infiltration. Citation Format: Jean-Philippe Guegan, Florent Peyraud, Christophe Rey, Oren Ngouala, Ophélie Odin, Imane Nafia, Isabelle Soubeyran, Sylvestre Le Moulec, Alban Bessede, Antoine Italiano. Indoleamine 2,3-dioxygenase 1 is highly expressed in tertiary lymphoid structures and associated with improved outcome in patients with advanced non-small cell lung cancer treated with anti-PD1/PDL1 inhibitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4341.

Abstract 6770: Spatial characterization of immune microenvironment from early onset metastatic colorectal cancer (EOmCRC) showed a dual prognostic role for IDO1 expression

Abstract Background: Epidemiological studies demonstrate that the incidence of CRC in young adults is continually rising in both Europe and the USA. The differences between the spatial distribution of immune related markers (IRM) and their prognostic role in EOmCRC compared to late onset (LOmCRC) remains to be elucidated. Methods: Forty paraffin embedded formalin fixed unstained sections from patients (pts) diagnosed with either EOmCRC (≤45) or (≥50) LOmCRC, matched for chemotherapy (chx) and molecular features, all with microsatellite stable disease were included. All tissue samples were obtained from pts enrolled in SPECTAcolor (EORTC-40CRC-GITCG) platform trial. The expression of IRM was studied using the GeoMX Digital Spatial Profiler (DSP). Fifty-seven IRMs were used and three morphology markers (MMs) anti-CD45, pan-cytokeratin and SYTO 13. Three 300 μm regions of interest (ROIs) were selected within the core of the tumour and further 3 ROIs within the active margin of the tumour. Each ROI was segmented based on MMs to obtain a tumour microenvironment (TME) and a tumour (T) mask. The analysis used the GeoMX DSP Advanced Analysis Suite software, R and IBM SPSS. Control for multiple comparisons use a false discovery rate (FDR) threshold of 0.05. Results: Samples from 40 pts were collected; 19 (47.5%) were EOmCRCs; 16 (40%) were female; 23 (57.5%) with pathological stage IV. The majority being, 23 (57.5%) grade ≥ 2, left sided 26 (65%), oxaliplatin based first line chx 23 (57.5%). Ten (25%) were KRAS mutant (mt), 1 (2.5%) NRAS mt and 1 (2.5%) BRAF mt. The median overall (OS) and progression free survival (PFS) for the entire cohort was 36.6 months (m) 95%CI (33.5 - 39.7) and 11.7 m (8.1 - 15.3), respectively.The <0.05 FDR differential expression analysis based on tissue segmentation uncovered 9 hits when comparing the TME between different age groups and 2 hits when comparing T segments, all overexpressed in LOmCRC. Indoleamine 2,3-dioxygenase 1 (IDO1) was differentially overexpressed in TME (adjusted p=0.043) and T (adjusted p=0.042) for LOmCRC.In the EOmCRC group IDO1 relative high expression in T was an independent marker associated with worse survival outcomes after multivariate cox regression corrected for the rest of significant markers (MVCC) for OS, HR: 7.01*105 95%CI (9.08*105-5.41*1010), p=0.003 and PFS, HR:7.7*105 95%CI (1.96-30.3*106), p=0.029. However, interestingly high IDO1 in TME was an independent marker associated with better OS, HR: 0.02 95%CI (0.01-0.46), p=0.015. Conclusion: Differential expression analysis of IRMs found IDO1 as differentially expressed in both segments (T and TME). Furthermore, high IDO1 expression seemed to have a dual prognostic role depending on the segment analysed, showing worse OS when found in the tumour but better OS when found in tumour microenvironment for early onset mCRC. Citation Format: Raghavendar Thyagaraja Nagaraju, Jakub Franczak, Markus Möhler, Elisa Fontana, Anne Giraut, Lieve Dirix, Jose Casas-Martin, Beatrice Borelli, Florian Lordick, Elizabeth Smith, Sabine Tejpar, Gunnar Folprecht, Jorge Barriuso. Spatial characterization of immune microenvironment from early onset metastatic colorectal cancer (EOmCRC) showed a dual prognostic role for IDO1 expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6770.

Abstract 2865: IL4I1, IDO1 and other amino acid-metabolizing enzymes in high-grade serous ovarian cancer

Abstract Ovarian cancer is among the most lethal malignancies in women, and breakthrough immunotherapies including anti-PD-1/PD-L1 and anti-CTLA4 have thus far not been able to significantly ameliorate patient outcomes. In various tumor types, amino acid-metabolizing enzymes such as indoleamine 2,3-dioxygenase 1 (IDO1) and arginase 1 (ARG1) have been found to be among the culprits responsible for generation of an immunosuppressive tumor microenvironment. More recently, interleukin 4 induced 1 (IL4I1) was put forward as a promising anticancer drug target, whereas its expression may also contribute to resistance against IDO1 inhibition. Similar to IDO1, IL4I1 can metabolize tryptophan (Trp) resulting in the formation of AhR agonists, although phenylalanine (Phe) and tyrosine (Tyr) are also major substrates of IL4I1. Plasma and ascites (i.e., peritoneal fluid buildup) were collected from advanced-stage high-grade serous ovarian cancer (HGSOC) patients to determine whether aberrant metabolism by amino acid-metabolizing enzymes occurs in these patients and to evaluate ascites as a potential source of biomarkers related to these enzymes. Activity of the enzymes was indirectly determined through measurement of relevant amino acids and metabolites by targeted metabolomics using LC-MS/MS, while levels of secreted IL4I1 were determined by ELISA. Amino acid, metabolite and enzyme concentrations were compared to healthy control subjects and were examined for correlations with clinicopathological characteristics and clinical outcomes. Pleural effusions from non-small cell lung cancer patients were included to evaluate whether the results could be extended towards another type of cancer-related fluid buildup. Metabolism of Trp was significantly elevated in HGSOC patients compared to control subjects, likely attributable to increased IDO1 expression. Kynurenine (Kyn) levels and Kyn/Trp ratios were higher in ascites compared to plasma samples, demonstrating the value of utilizing this fluid for biomarker detection. Whereas elevated metabolism of Trp by IL4I1 could not be detected in the patients, high levels of Phe- and Tyr-derived metabolites associated with IL4I1 activity were found in their ascites. Levels of these metabolites significantly correlated with the concentration of IL4I1. Moreover, enhanced metabolism of Phe and Tyr correlated with disease stage, suggesting a role for IL4I1 in HGSOC progression. Elevated levels of IL4I1-associated metabolites were also found in the pleural effusions of a subset of non-small cell lung cancer patients, demonstrating that enhanced IL4I1 activity is not limited to ovarian cancer ascites. In conclusion, our results suggest that IL4I1 may be involved in HGSOC progression, indicating this enzyme as a potential therapeutic target. The levels of IL4I1- and IDO1-generated metabolites in ascites may additionally serve as valuable diagnostic or predictive biomarkers. Citation Format: Yvonne Grobben, Judith E. den Ouden, Cristina Aguado, Anne M. van Altena, Aletta D. Kraneveld, Guido J. Zaman. IL4I1, IDO1 and other amino acid-metabolizing enzymes in high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2865.

Thermosusceptible Nitric-Oxide-Releasing Nitrogel for Strengthening Antitumor Immune Responses with Tumor Collagen Diminution and Deep Tissue Delivery during NIR Laser-Assisted Photoimmunotherapy.

Combined cancer immunotherapy has demonstrated promising potential with an amplified antitumor response and immunosuppressive tumor microenvironment (TME) modulation. However, one of the main issues that cause treatment failure is the poor diffusion and insufficient penetration of therapeutic and immunomodulatory agents in solid tumors. Herein, a cancer treatment approach that combines photothermal therapy (PTT) and nitric oxide (NO) gas therapy for tumor extracellular matrix (ECM) degradation, along with NLG919, an indoleamine 2,3-dioxygenase (IDO) inhibitor that reduces tryptophan catabolism to kynurenine, and DMXAA, a stimulator of interferon gene (STING) agonist that stimulates antigen cross-presentation, is proposed to overcome this issue. Upon NIR (808 nm) laser irradiation, NO-GEL achieved the desired thermal ablation by releasing sufficient tumor antigens through immunogenic cell death (ICD). NO delivery triggered local diffusion of excess NO gas for effectively degrading tumor collagen in the ECM, homogeneously delivered NLG919 throughout the tumor tissue, inhibited IDO expression that was upregulated by PTT, and reduced the immune suppressive activities. The sustained release of DMXAA prolonged dendritic cell maturation and CD8+ T cell activation against the tumor. In summary, NO-GEL therapeutics offer a significant tumor regression with PTT and STING agonist combination that stimulates a durable antitumor immune response. Additional unification of IDO inhibition during PTT supplements the immunotherapy by reducing the T cell apoptosis and immune suppressive cell infiltration to TME. NO-GEL with the STING agonist and IDO inhibitor is an effective therapeutic combination to counter possible limitations during solid tumor immunotherapy.

Interleukin-6 promotes skeletal muscle catabolism by activating tryptophan-indoleamine 2,3-dioxygenase 1-kynurenine pathway during intra-abdominal sepsis.

Inflammatory cytokine interleukin-6 (IL-6) plays a pivotal role in skeletal muscle degradation after intra-abdominal sepsis (IAS), with mechanism remained to be elucidated. Indoleamine 2,3-dioxygenase 1 (IDO-1), a key enzyme in converting tryptophan into kynurenine, could be activated by IL-6, and kynurenine has been shown to be involved in muscle degradation. We hypothesized that IL-6 could promote muscle degradation via tryptophan-IDO-1-kynurenine pathway in IAS patients. Serum and rectus abdominis (RA) were obtained from IAS or non-IAS patients. Mouse model of IAS-induced muscle wasting was generated by caecal ligation and puncture (CLP) and lipopolysaccharide (LPS) injection. IL-6 signalling was blocked by anti-mouse IL-6 antibody (IL-6-AB), and the IDO-1 pathway was blocked by navoximod. To elucidate the role of kynurenine in muscle mass and physiology, kynurenine was administered to IAS mice treated with IL-6-AB. Compared to non-IAS patients, kynurenine levels in serum (+2.30-fold vs. non-IAS, P<0.001) and RA (+3.11-fold vs. non-IAS, P<0.001) were elevated, whereas tryptophan levels in serum (-53.65% vs. non-IAS, P<0.01) and RA (-61.39% vs. non-IAS, P<0.01) were decreased. Serum IL-6 level of the IAS group was significantly higher compared to non-IAS patients (+5.82-fold vs. non-IAS, P=0.01), and muscle cross-sectional area (MCSA) was markedly reduced compared to non-IAS patients (-27.73% vs. non-IAS, P<0.01). In animal experiments, IDO-1 expression was up-regulated in the small intestine, colon and blood for CLP or LPS-treated mice, and there was correlation (R2 =0.66, P<0.01) between serum and muscle kynurenine concentrations. Navoximod significantly mitigated IAS-induced skeletal muscle loss according to MCSA analysis (+22.94% vs. CLP, P<0.05; +23.71% vs. LPS, P<0.01) and increased the phosphorylated AKT (+2.15-fold vs. CLP, P<0.01; +3.44-fold vs. LPS, P<0.01) and myosin heavy chain (+3.64-fold vs. CLP, P<0.01; +2.13-fold vs. LPS, P<0.01) protein expression in myocytes. In the presence of anti-IL-6 antibody, a significantly decreased IDO-1 expression was observed in the small intestine, colon and blood in CLP or LPS mice (all P<0.01), whereas the decrease of MCSA was alleviated (+37.43% vs. CLP+IgG, P<0.001; +30.72% vs. LPS+IgG, P<0.001). In contrast, additional supplementation of kynurenine decreased the MCSA in septic mice treated with IL-6-AB (both P<0.01). This study provided novel insights into the tryptophan-IDO-1-kynurenine-dependent mechanisms that underlie inflammatory cytokine-induced skeletal muscle catabolism during intra-abdominal sepsis.

Bone marrow mesenchymal stem cell-derived exosomes attenuate the maturation of dendritic cells and reduce the rejection of allogeneic transplantation

Bone mesenchymal stem cell (BMSC)-derived exosomes (B-exos) are attractive for applications in enabling alloantigen tolerance. An in-depth mechanistic understanding of the interaction between B-exos and dendritic cells (DCs) could lead to novel cell-based therapies for allogeneic transplantation. To examine whether B-exos exert immunomodulatory effects on DC function and maturation. After mixed culture of BMSCs and DCs for 48 h, DCs from the upper layer were collected to analyze the expression levels of surface markers and mRNAs of inflammation-related cytokines. Then, before being collected to detect the mRNA and protein expression levels of indoleamine 2,3-dioxygenase (IDO), the DCs were co-cultured with B-exos. Then, the treated DCs from different groups were co-cultured with naïve CD4+ T cells from the mouse spleen. The proliferation of CD4+ T cells and the proportion of CD4+CD25+Foxp3+ T cells were analyzed. Finally, the skins of BALB/c mice were transplanted to the back of C57 mice in order to establish a mouse allogeneic skin transplantation model. The co-culture of DCs with BMSCs downregulated the expression of the major histocompatibility complex class II (MHC-II) and CD80/86 costimulatory molecules on DCs. Moreover, B-exos increased the expression of IDO in DCs treated with lipopolysaccharide (LPS). The proliferation of CD4+CD25+Foxp3+ T cells increased when cultured with B-exos-exposed DCs. Finally, mice recipients injected with B-exos-treated DCs had significantly prolonged survival after receiving the skin allograft. Taken together, these data suggest that the B-exos suppress the maturation of DCs and increase the expression of IDO, which might shed light on the role of B-exos in inducing alloantigen tolerance.

Rifaximin ameliorates depression-like behaviour in chronic unpredictable mild stress rats by regulating intestinal microbiota and hippocampal tryptophan metabolism

BackgroundChronic unpredictable mild stress (CUMS) can induce depressive behaviours and alter the composition of the gut microbiome. Although modulating gut microbiota can improve depression-like behaviour in rats, the mechanism of action is unclear. Additionally, gut microbiota can affect brain function through the neuroendocrine pathway. This pathway may function by regulating the secretion of neurotransmitters such as tryptophan (TRP). Metabolites of TRP, such as 5-hydroxytryptamine (5-HT) and kynurenine (KYN), are related to the pathophysiological process of depression. Indoleamine-2, 3-dioxygenase-1 (IDO1) and Tryptophan hydroxylase 2 (TPH2) are the key rate-limiting enzymes in TRP metabolism and play an important role in KYN and 5-HT metabolism. MethodsRats were subjected to four weeks of CUMS and given rifaximin150 mg/kg by oral gavage daily. After modelling, we investigated the rat's behaviours, composition of the faecal microbiome, neurotransmitter metabolism and key metabolic enzymes of the TRP pathway in the hippocampus (HIP). ResultsRifaximin administration improved depressive behaviour in rats, corrected intestinal microbiota disorders and HIP TRP metabolism and regulated the expression of IDO1 and TPH2 in the HIP. ConclusionsRifaximin improves depression-like behaviour in CUMS rats by influencing the gut microbiota and tryptophan metabolism.

Engineered Living Bacteriophage-Enabled Self-Adjuvanting Hydrogel for Remodeling Tumor Microenvironment and Cancer Therapy.

Due to the complexity and heterogeneity in the tumor microenvironment, the efficacy of breast cancer treatment has been significantly impeded. Here, we established a living system using an engineered M13 bacteriophage through chemical cross-linking and biomineralization to remodel the tumor microenvironment. Chemically cross-linking of the engineered bacteriophage gel (M13 Gel) could in situ synthesize photothermal palladium nanoparticles (PdNPs) on the pVIII capsid protein to obtain M13@Pd Gel. In addition, NLG919 was further loaded into a gel to form (M13@Pd/NLG gel) for down-regulating the expression of tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1). Both in vitro and in vivo studies showed that the M13 bacteriophage served not only as a cargo-loaded device but also as a self-immune adjuvant, which induced the immunogenic death of tumor cells effectively and down-regulated IDO1 expression. Such a bioactive gel system constructed by natural living materials could reverse immunosuppression and significantly improve the anti-breast cancer response.

Tryptophan degradation enzymes expression in the placenta and the Kynurenine/Tryptophan ratio in maternal plasma after elective cesarean section

Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO) metabolize tryptophan in the kynurenine pathway. We evaluated these enzymes’ mRNA expression in maternal and fetal sides of the placenta of uncomplicated, unlabored full-term pregnancies after elective cesarean section and compared it with that of placentas obtained from vaginal delivery. Tryptophan and kynurenine plasmatic levels after cesarean section were measured, to investigate their possible correlation with IDO1 and TDO mRNA (TDO2) expression. The results suggested that IDO1 and TDO2 expression was higher in the maternal side of the placenta and that labor significantly affects TDO2 expression and the plasma Kynurenine/Tryptophan ratio.

Inhibition of indoleamine dioxygenase leads to better control of tuberculosis adjunctive to chemotherapy.

The expression of indoleamine 2,3-dioxygenase (IDO), a robust immunosuppressant, is significantly induced in macaque tuberculosis (TB) granulomas, where it is expressed on IFN-responsive macrophages and myeloid-derived suppressor cells. IDO expression is also highly induced in human TB granulomas, and products of its activity are detected in patients with TB. In vivo blockade of IDO activity resulted in the reorganization of the granuloma with substantially greater T cells being recruited to the core of the lesions. This correlated with better immune control of TB and reduced lung M. tuberculosis burdens. To study if the IDO blockade strategy can be translated to a bona fide host-directed therapy in the clinical setting of TB, we studied the effect of IDO inhibitor 1-methyl-d-tryptophan adjunctive to suboptimal anti-TB chemotherapy. While two-thirds of controls and one-third of chemotherapy-treated animals progressed to active TB, inhibition of IDO adjunctive to the same therapy protected macaques from TB, as measured by clinical, radiological, and microbiological attributes. Although chemotherapy improved proliferative T cell responses, adjunctive inhibition of IDO further enhanced the recruitment of effector T cells to the lung. These results strongly suggest the possibility that IDO inhibition can be attempted adjunctive to anti-TB chemotherapy in clinical trials.

Targeting Lin28 axis enhances glypican-3-CAR T cell efficacy against hepatic tumor initiating cell population

Overexpression of Lin28 is detected in various cancers with involvement in the self-renewal process and cancer stem cell generation. In the present study, we evaluated how the Lin28 axis plays an immune-protective role for tumor-initiating cancercells in hepatocellular carcinoma (HCC). Our result usingHCC patient samples showed a positive correlation between indoleamine 2,3-dioxygenase-1 (IDO1), a kynurenine-producing enzyme with effects on tumor immune escape, andLin28B. Using in silico prediction, we identified a Sox2/Oct4 transcriptional motif acting as an enhancer for IDO1. Knockdown of Lin28B reduced Sox2/Oct4 and downregulated IDO1 in tumor-initiating hepatic cancer cells. We further observed that inhibition of Lin28 by a small-molecule inhibitor(C1632) suppressed IDO1 expression. Suppression of IDO1 resulted in a decline in kynurenine production from tumor-initiating cells. Inhibition of the Lin28 axis also impaired PD-L1 expression in HCC cells. Consequently, modulating Lin28B enhanced invitro cytotoxicity of glypican-3 (GPC3)-chimeric antigen receptor (CAR) T and NK cells. Next, we observed that GPC3-CAR Tcell treatment together with C1632 in a HCC xenograft mouse model led to enhanced anti-tumor activity. In conclusion, our results suggest that inhibitionof Lin28B reduces IDO1 and PD-L1 expression and enhances immunotherapeutic potential of GPC3-CART cells against HCC.

A novel pathologic marker, indoleamine 2,3-dioxygenase 1, for the cholangiopathy of immune checkpoint inhibitors-induced immune mediated hepatotoxicity as adverse events and the prediction of additional ursodeoxycholic acid treatment.

Immune-related adverse events (irAE) has been clarified according the usage of immune checkpoint inhibitors(ICI). We primarily found indoleamine 2,3-dioxygenase 1(IDO-1) as a histologic biomarker for the cholangiopathy of primary biliary cholangitis(PBC). In this study, we evaluated the utility of IDO-1 in identifying ICI-induced immune-mediated hepatotoxicity(IMH). Immunostaining for IDO-1 using liver sections of PBC, ICI-induced IMH and controls, revealed that IDO-1 expression in bile ducts is mostly restricted in PBC and ICI-induced IMH. In ICI-induced IMH, IDO-1-positive bile ducts is found in 2/2 cases of cholangitis type and also positive/focal ducts in 11/15 cases of hepatitis type. Moreover, in 8/13 positive/focal cases, ursodeoxycholic acid as well as steroids were needed to improve liver dysfunction, but just one case (1/4) in IDO-1-negative cases. One IDO-1 positive case of hepatitis type did not receive additional UDCA, but biliary enzymes worsen. In vitro study using cultured human biliary epithelial cells revealed that IDO-1 induction was found with the stimulation of IFN-γ. In conclusion, the presence of IDO-1-positive cells is found in bile ducts in hepatitic type as well as sclerosing cholangitis of ICI-induced IMH. IDO-1 is surely a valuable pathologic marker for diagnosing ICI-induced IMH and also for predicting an additional need of UDCA in clinical practice.

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.

Endothelial Indoleamine-2,3-Dioxygenase-1 is not Critically Involved in Regulating Antitumor Immunity in the Central Nervous System.

The vascular niche of malignant gliomas is a key compartment that shapes the immunosuppressive brain tumor microenvironment (TME). The blood-brain-barrier (BBB) consisting of specialized endothelial cells (ECs) and perivascular cells forms a tight anatomical and functional barrier critically controlling transmigration and effector function of immune cells. During neuroinflammation and tumor progression, the metabolism of the essential amino acid tryptophan (Trp) to metabolites such as kynurenine has long been identified as an important metabolic pathway suppressing immune responses. Previous studies have demonstrated that indoleamine-2,3-dioxygenase-1 (IDO1), a key rate-limiting enzyme in tryptophan catabolism, is expressed within the TME of high-grade gliomas. Here, we investigate the role of endothelial IDO1 (eIDO1) expression for brain tumor immunity. Single-cell RNA sequencing data revealed that in human glioma tissue, IDO1 is predominantly expressed by activated ECs showing a JAK/STAT signaling pathway-related CXCL11+ gene expression signature. In a syngeneic experimental glioma model, eIDO1 is induced by low-dose tumor irradiation. However, cell type-specific ablation of eIDO1 in experimental gliomas did not alter frequency and phenotype of tumor-infiltrating T cells nor tumor growth. Taken together these data argue against a dominant role of eIDO1 for brain tumor immunity.

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.

Effect of apigenin on tryptophan metabolic key enzymes expression in lipopolysaccharide-induced microglial cells and its mechanism

[Aims] Flavonoid apigenin (API) has a wide range of biological functions, particularly anti-inflammation. Indoleamine 2,3-dioxygenase (IDO) and 2-Amino-3-carboxymuconate-6-semialdehyde decarboxylase (ACMSD) are important tryptophan metabolic enzymes that play pivotal roles in the production of toxic metabolite quinolinic acid. However, the relationship between inflammation and ACMSD remains unclear. The present study investigated the relationship between inflammation and tryptophan metabolic key enzymes. Similarly, the anti-inflammatory effect of API on important tryptophan metabolic enzymes was examined in lipopolysaccharide (LPS)-treated microglial cells.[Main methods] MG6 cells were exposed to LPS with or without API treatment for 24–48 h. IDO and ACMSD mRNA expression and production of inflammatory mediators were analyzed. Activation of inflammatory signaling pathways, such as mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB), was also examined to study the mechanism of API in the inflammatory state.[Key findings] LPS suppressed ACMSD expression and enhanced IDO expression. However, API elevated ACMSD mRNA expression and suppressed IDO mRNA expression in LPS-treated MG6 cells. Furthermore, API suppressed interleukin-6 and nitric oxide production, whereas overproduction of inflammatory mediators enhanced IDO expression and assisted tryptophan degradation. API also inhibited activation of extracellular signal-regulated kinase (Erk) and jun N-terminal kinase (JNK) MAPK, and degradation of IκBα.[Significance] These results indicate alteration of ACMSD expression under inflammatory conditions. Moreover, API recovers expression of tryptophan metabolic key enzymes, which may be mediated by inhibition of proinflammatory mediator production via inactivation of Erk, JNK MAPK, and NF-κB pathways in LPS-stimulated microglial cells.

IDO-1 inhibitor INCB24360 elicits distant metastasis of basal extruded cancer cells in pancreatic ductal adenocarcinoma

Neoplastic cells of non-immunogenic pancreatic ductal adenocarcinoma (PDAC) express indoleamine 2,3-dioxygenase 1 (IDO-1), an immunosuppressive enzyme. The metabolites of IDO-1 in cancers provide one-carbon units that annihilate effector T cells, and recruit immunosuppressive cells. In this study we investigated how IDO-1 affected the neoplastic cell behaviors in PDACs. Using multiple markers co-labeling method in 45-µm-thick tissue sections, we showed that IDO-1 expression was uniquely increased in the neoplastic cells extruded from ducts’ apical or basal domain, but decreased in lymph metastatic cells. IDO-1+ extruding neoplastic cells displayed increased vimentin expression and decreased cytokeratin expression in PDACs, characteristics of epithelial-mesenchymal transition (EMT). However, IDO-1 expression was uncorrelated with immunosuppressive infiltrates and clinicopathological characteristics of grim outcome. We replicated basal extrusion with EMT in murine KPIC PDAC organoids by long-term IFN-γ induction; application of IDO-1 inhibitor INCB24360 or 1-MT partially reversed basal extrusion coupled EMT. Ido-1 deletion in KPIC cells deprived its tumorigenicity in immunocompetent mice, decreased cellular proliferation and macropinocytic ability, and increased immunogenicity. KPIC organoids with IFN-γ-induced basal extrusion did not accelerate distant metastasis, whereas inhibition IFN-γ-induced IDO-1 with INB24360 but not 1-MT in KPIC organoids elicited liver metastasis of subcutaneous KPIC organoid tumors, suggesting that lower IDO-1 activity accelerated distant metastasis, whereas IDO-1 was indispensable for tumorigenicity of PDAC cells and supports the survival of extruding cells.