Indoleamine 2,3-dioxygenase Inhibitor Research Articles

Indoleamine 2,3-dioxygenase in melanoma progression and BRAF inhibitor resistance

Indoleamine 2,3-dioxygenase (IDO) is associated with the progression of many types of tumors, including melanoma. However, there is limited information about IDO modulation on tumor cell itself and the effect of BRAF inhibitor (BRAFi) treatment and resistance. Herein, IDO expression was analyzed in different stages of melanoma development and progression linked to BRAFi resistance. IDO expression was increased in primary and metastatic melanomas from patients’ biopsies, especially in the immune cells infiltrate. Using a bioinformatics approach, we also identified an increase in the IDO mRNA in the vertical growth and metastatic phases of melanoma. Using in silico analyses, we found that IDO mRNA was increased in BRAFi resistance. In an in vitro model, IDO expression and activity induced by interferon-gamma (IFNγ) in sensitive melanoma cells was decreased by BRAFi treatment. However, cells that became resistant to BRAFi presented random IDO expression levels. Also, we identified that treatment with the IDO inhibitor, 1-methyltryptophan (1-MT), was able to reduce clonogenicity for parental and BRAFi-resistant cells. In conclusion, our results support the hypothesis that the decreased IDO expression in tumor cells is one of the many additional outcomes contributing to the therapeutic effects of BRAFi. Still, the IDO production changeability by the BRAFi-resistant cells reiterates the complexity of the response arising from resistance, making it not possible, at this stage, to associate IDO expression in tumor cells with resistance. On the other hand, the maintenance of 1-MT off-target effect endorses its use as an adjuvant treatment of melanoma that has become BRAFi-resistant.

Kynurenine pathway modulation reverses the experimental autoimmune encephalomyelitis mouse disease progression

BackgroundMultiple sclerosis (MS) is a chronic immune-mediated disorder of the central nervous system characterized by demyelination, neuroinflammation, and neurodegeneration. Activation of the kynurenine pathway (KP) results from acute and chronic neuroinflammation leading to both immune suppression and neurotoxicity. However, the exact effects of KP metabolites and changes in neurodegenerative diseases over time are not fully understood. Studies, including those in MS models, have reported that short-term KP activation is beneficial through immune tolerance. However, the effects of long-term KP activation are poorly understood. We hypothesized that such chronic activation is responsible for the neurodegeneration in MS, and further, modulating the KP in EAE-induced mice could significantly decrease the EAE disease severity.MethodsWe biochemically altered the KP at different stages of the disease in experimental allergic encephalomyelitis (EAE) mouse model of MS and at two different enzymatic levels of the KP (IDO-1 (indoleamine 2,3 dioxygenase)) and KMO (kynurenine monooxygenase). CNS tissue and blood samples were analyzed longitudinally using GCMS, HPLC, IHC, and RT-PCR.ResultsWe showed that the KP was steadily upregulated correlating with disease severity and associated with a shift towards increasing concentrations of the KP metabolite quinolinic acid, a neuro- and gliotoxin. KP modulation by inhibition of IDO-1 with 1-methyl tryptophan (1-MT) was dependent on the timing of treatment at various stages of EAE. IDO-1 inhibition at EAE score 2 led to significantly higher numbers of FoxP3 cells (p < 0.001) in the spleen than earlier IDO-1 inhibition (prophylactic 1-MT treatment group (p < 0.001)), 1-MT treatment after EAE induction (EAE score 0; p < 0.001), and 1-MT treatment at EAE score of 1 (p < 0.05). Significant improvement of disease severity was observed in EAE mice treated with 1-MT at EAE score 2 compared to the untreated group (p < 0.05). KP modulation by KMO inhibition with Ro 61-8048 led to significantly greater numbers of Foxp3 cells (p < 0.05) in Ro 61-8048 treated mice and even more significant amelioration of EAE disease compared to the 1-MT treatment groups.ConclusionsThese results provide a new mechanistic link between neuroinflammation and neurodegeneration and point to KP modulation at the KMO level to preserve immune tolerance and limit neurodegeneration in EAE. They provide the foundation for new clinical trials for MS.

L-Tryptophan-Induced Vasodilation Is Enhanced in Preeclampsia: Studies on Its Uptake and Metabolism in the Human Placenta.

l-tryptophan induces IDO (indoleamine 2,3-dioxygenase) 1-dependent vasodilation. IDO1 is expressed in placental endothelial cells and downregulated in preeclampsia. Hypothesizing that this may contribute to diminished placental perfusion, we studied l-tryptophan-induced vasodilation in healthy and early-onset preeclampsia placental arteries, focusing on placental kynurenine pathway alterations. Despite IDO1 downregulation, kynurenine pathway metabolite concentrations (measured with ultra-performance liquid chromatography-tandem mass spectrometry) were unaltered in preeclamptic versus healthy placentas. Most likely, this is due to enhanced l-tryptophan uptake, evidenced by increased l-tryptophan levels in preeclamptic placentas. Ex vivo perfused cotyledons from healthy and preeclamptic placentas released similar amounts of l-tryptophan and kynurenine pathway metabolites into the circulations. This release was not altered by adding l-tryptophan in the maternal circulation, suggesting that l-tryptophan metabolites act intracellularly. Maternally applied l-tryptophan did appear in the fetal circulation, confirming placental passage of this essential amino acid. After in vitro incubation of placental arteries with IDO1-upregulating cytokines interferon-γ and tumor necrosis factor-α, l-tryptophan induced vasodilation. This vasodilation was attenuated by both IDO1 and nitric oxide (NO) synthase inhibitors. Despite IDO1 downregulation, l-tryptophan-induced relaxation was enhanced in preeclamptic versus healthy placental arteries. However, cytokine stimulation additionally upregulated the LAT (l-type amino acid transporter) 1 in preeclamptic placental arteries only. Vasodilation to the lipophilic, transporter independent ethyl ester of l-tryptophan was reduced in preeclamptic versus healthy placental arteries, in agreement with reduced IDO1 expression. In conclusion, l-tryptophan induces IDO1- and NO-dependent relaxation in placental arteries, which is determined by l-tryptophan uptake rather than IDO1 expression. Increased l-tryptophan uptake might compensate for reduced IDO1 expression in preeclamptic placentas.

Increased effect of two-fractionradiotherapy in conjunction with IDO1 inhibition in experimental glioblastoma.

ObjectivesThe aim of the study was to investigate therapeutic efficacy of single- or two-fraction radiotherapy in conjunction with IDO1-inhibition in a syngeneic rat glioblastoma model. IDO is known to cause immunosuppression through breakdown of tryptophan in the tumor microenvironment.MethodsGene expression analyses of IDO in glioblastoma were performed with data from publicly available datasets. Fractionation studies were done on animals to evaluate tumor size, immune cell infiltration of tumors and serum profile on day 18 after tumor inoculation. Survival analyses were done with animals carrying intracranial glioblastomas comparing two-fraction radiotherapy+IDO1-inhibition to controls. IDO inhibition was achieved by administration of 1-methyl tryptophan (1-MT), and radiotherapy (RT) was delivered in doses of 8Gy.ResultsThe expression of IDO1 was increased on gene level in glioblastoma stem cells. Tumor size was significantly reduced in animals treated with 1-MT+RTx 2 (both long and short intervals, i.e. 7 and 4 days between the treatments) as compared to control animals, animals treated with only 1-MT or animals treated with 1-MT+RTx1. Serum levels of IL-1A were significantly altered in all treated animals as compared to control animals. Survival was significantly increased in the animals treated with 1-MT+RTx2 (7-day interval) compared to control animals.ConclusionsAddition of two-fraction RT to IDO1 inhibition with 1-MT significantly reduced tumor size in animals with glioblastoma. Survival was significantly increased in animals treated with two-fractioned RT+1-MT as compared to untreated controls increased significantly.Advances in knowledgeThe currently used combination of only two fractions of radiotherapy and immune therapy is a promising area of research, increasing efficacy compared to single fraction irradiation, while potentially lowering radiation side effects compared to radiation in current clinical practice.

The Advances of the Structure and Function of Indoleamine 2, 3- dioxygenase 1 and Its Inhibitors.

Indoleamine 2, 3-dioxygenase 1 (IDO1) is the only rate-limiting enzyme outside the liver that catalyzes the oxidation and cracking of indole rings in the tryptophan along the kynurenine pathway (KP). The overactivation of IDO1 is closely related to the pathogenesis of various human immune and neurological diseases. As an important target for the treatment of many human serious diseases, including malignant tumors, the development of IDO1 inhibitors is of great practical significance. In this work, the structure and function of IDO1 both are summarized from the aspects of the signal pathway, catalytic mechanism, structural biology, and so on. Moreover, the current development status of IDO1 inhibitors is also systematically reviewed, which provides assistance for anti-cancer drug design based on the structure of receptors.

Increased Expression of Indoleamine 2,3-Dioxygenase (IDO) in Vogt-Koyanagi-Harada (VKH) Disease May Lead to a Shift of T Cell Responses Toward a Treg Population.

Previous studies have pointed out that indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme initiating tryptophan metabolism, plays a role in the regulation of the immune system. This project was designed to investigate the potential role of IDO in monocyte-derived dendritic cells (moDCs) obtained from active Vogt-Koyanagi-Harada (VKH) disease patients. In this study, we found that the IDO mRNA expression and enzyme activity were increased in active VKH patients as compared with healthy controls and patients in remission. To investigate the role of IDO in immune regulation, an effective inhibitor 1-methyl-L-tryptophan (1-MT) was used to suppress its activity in DCs. The results showed that inhibition of IDO with 1-MT significantly decreased the expression of DC marker CD86. IDO inhibition did not affect the cytokine production of IL-6, IL-1β, TNF-α, IL-10, and TGF-β in DCs. Downregulation of IDO in DCs also led to the reduction of regulatory T (Treg) cells and an increased CD4+ T cell proliferation. Treatment with 1-MT did not affect the phosphorylation of the MAPK pathway in DCs. In general, our study suggests that IDO may play an important role in the pathogenesis of VKH disease by regulating DC and CD4+ T cell function. Tryptophan deficiency and kynurenine accumulation may account for the complicated effects of IDO. Further research is needed to study the precise tryptophan metabolites that may limit immune responses in VKH disease.

Window-of-opportunity trial of nivolumab with or without the IDO inhibitor BMS-986205 in patients with resectable squamous cell carcinoma of the head and neck (SCCHN).

TPS6595 Background: Indoleamine 2,3-dioxygenase (IDO1) catabolizes tryptophan to kynurenine and is highly expressed in multiple malignancies including SCCHN. Elevated IDO1 activity may contribute to an immunosuppressive tumor microenvironment and compromise therapeutic responses to immune checkpoint therapy. We designed a window-of-opportunity trial to test whether the IDO inhibitor BMS-986305 improves treatment responses and T cell function in SCCHN patients treated with nivolumab. Methods: Patients with previously untreated, resectable, pathologically confirmed SCCHN are eligible. Primaries of the oral cavity, oropharynx, larynx, hypopharynx, or nasal cavity/paranasal sinuses must be AJCC 8th edition stage II or higher (M0). Stage I oropharyngeal cancers with lymphadenopathy are also eligible. Patients are randomized 3:1 to receive either A) nivolumab 480 mg IV x 1 plus BMS-986205 100 mg PO daily starting a week prior to nivolumab and continuing for 4 more weeks (total of 5 weeks) or B) nivolumab 480 mg IV alone for 4 weeks. At the 5th week of treatment patients are assessed for response with physical exam and repeat CT scans for tumor volumes: if there is greater than 10% reduction in volume of either primary tumor or lymph node metastases, patients will be considered responders and receive another cycle of their originally assigned treatment, i.e. nivolumab 480 mg IV for a second dose +/- BMS-986205 100 mg PO daily for an additional 4 weeks followed by surgery in week 9. If tumor volume is stable or progression is noted in either the primary site or lymph nodes, patients are considered non-responders followed by definitive surgery in week 5 (i.e. after only one cycle of treatment). The primary endpoint of this study is the response rate after cycle 1 (using the criteria defined above). The projected sample size is 48 patients (36 in arm A and 12 in arm B). Secondary endpoints include safety, pathologic treatment effect and metabolic and molecular correlates of treatment in the tumor microenvironment. Clinical trial information: NCT03854032 .

A phase II, randomized study of nivolumab (NIVO), NIVO plus linrodostat mesylate, or NIVO plus intravesical bacillus Calmette-Guerin (BCG) in BCG-unresponsive, high-risk, nonmuscle invasive bladder cancer (NMIBC): CheckMate 9UT.

TPS5090 Background: Immune checkpoint inhibitors, including NIVO (anti–PD-1), have demonstrated favorable tolerability and efficacy profiles, ushering in a new treatment (tx) paradigm for advanced bladder cancer (advBC). However, an unmet need exists for new effective tx options in earlier stages of disease, specifically for patients (pts) with BCG-unresponsive, high-risk NMIBC. Increased IDO and PD-L1 expression in NMIBC tumors (Inman, et al. Cancer 2007; Hudolin, et al. Anticancer Res 2017), support the combination of anti–PD-1 and IDO1 inhibition in NMIBC. Linrodostat mesylate, a selective, potent, once-daily IDO1 inhibitor, has demonstrated clinical activity in combination with NIVO in pts with immunotherapy-naive advBC who received ≥ 1 prior line of therapy (objective response rate, 37%; Tabernero, et al. J Clin Oncol 2018;36(suppl) [abstr 4512]). Furthermore, high levels of PD-L1 expression have been reported in patients not responding to BCG tx. These findings provide a rationale for investigation of NIVO ± linrodostat ± intravesical BCG therapy in BCG-unresponsive high-risk NMIBC. Here we describe a phase 2, randomized, open-label study assessing the safety and efficacy of NIVO ± linrodostat ± intravesical BCG in pts with BCG-unresponsive, high-risk NMIBC (NCT03519256). Methods: Pts aged ≥ 18 years with BCG-unresponsive (per February 2018 FDA guidance), high-risk NMIBC, defined as carcinoma-in-situ (CIS) with or without papillary component, any T1, or Ta high-grade lesions, will be enrolled. Pts must have urothelial carcinoma as the predominant histological component ( &gt; 50%). Key exclusion criteria include locally advanced or metastatic BC, upper urinary tract disease within 2 years, prostatic urethral disease within 1 year, and prior immunotherapy. Using a novel adaptive-type design, pts will be randomized to 1 of 4 tx arms with NIVO ± linrodostat ± BCG. Primary endpoints include proportion of pts with CIS with complete response (CR) and duration of CR in pts with CIS. Secondary endpoints are progression-free survival and safety. This global study in 14 countries is underway, with a target enrollment of 436 pts. Clinical trial information: NCT03519256 .

The study on the effect of depression on breast cancer incidence through IDO/kynurenine pathway.

e13569 Background: Psychosocial factors have been considered as the most common causes for women with breast cancer. However, it remains unclear whether mental stress can influence cancer incidence and progression. This study aims to investigate the relationship between them and the potential molecular mechanism. Methods: Depression model was established by restricting MMTV-PyMT mice in a 50ml-fixator for 4 h per day for 21 consecutive days. Behavioral tests including light-dark box test, open-field test and force swimming test were performed. Then blood, brain and mammary samples were collected at the indicated time points. ELISA was used to detect the concentration of neurotransmitters serotonin, epinephrine and norepinephrine and inflammatory factors IL-6, TNF-a and IL-1β in brain tissue and serum. Real-time quantitative qPCR and western blot were used to detect indoleamine 2, 3-dioxygenase (IDO) expression. The level of tryptophan was measured by high performance liquid chromatography(HPLC). Flow cytometry was used to evaluate the exhaustion of CD8+ T cells. Besides, the correlation between IDO expression detected by immunohistochemistry and the severity of mammary tumors was analyzed in the tumor specimens. Results: We observed that chronic stress caused depression-like behaviors, abnormal secretion of neurotransmitters serotonin, epinephrine and norepinephrine and promoted the development of breast cancer in MMTV-PyMT mice. Depression elevated the secretion of inflammatory factors IL-6, TNF-a and IL-1β in brain tissue and serum, which upregulated the expression of IDO and decreased the level of tryptophan in mice. Furthermore, T cells are sensitive to low tryptophan concentration, so elevated IDO expression suppressed and exhausted CD8+ T cells, ultimately promoting cancer incidence. Administration of xiaoyao pill (a well-known Chinese herbal formula for treating depression) or IDO inhibitor reversed the depression-like behaviors in mice and slowed the development of breast cancer. At the same time, the analysis of clinical samples showed that depression identified by Hamilton Depression Scale(HAMD) and IDO expression in mammary tumor tissues were positively correlated with the severity of mammary tumors. Conclusions: Altogether, our results suggest that depression can promote tumor immune privilege and cancer occurrence through inducing upregulated IDO expression.

A phase III randomized study of neoadjuvant chemotherapy (NAC) alone or in combination with nivolumab (NIVO) ± linrodostat mesylate, followed by adjuvant postsurgical NIVO ± linrodostat, in cisplatin-eligible muscle invasive bladder cancer (MIBC).

TPS5091 Background: Immuno-oncology (IO) therapies have revolutionized the treatment (tx) of pts with advanced bladder cancer (advBC). For pts with cisplatin-eligible, muscle invasive BC (MIBC), the recommended tx is cisplatin-based neoadjuvant chemotherapy (NAC) prior to radical cystectomy (RC). However, since only ≈ 30% of pts achieve a pathologic complete response (pCR) translating to improved long-term outcomes with approved regimens, new therapies are needed. PD-L1 expression is associated with aggressive BC and has been shown to increase in BC after NAC, supporting the therapeutic pursuit of the PD-1/PD-L1 axis. Additionally, expression of indoleamine 2,3-dioxygenase (IDO) is higher in BC than in normal bladder tissue and is associated with advanced disease and poor clinical outcome. Linrodostat mesylate, a selective, potent, once-daily oral IDO1 inhibitor that works to reduce kynurenine production, has demonstrated clinical activity in combination with NIVO (anti–PD-1) in pts with IO tx–naive advBC who had ≥ 1 prior line of therapy (ORR, 37%). Taken together, these data provide a rationale for investigating NAC + NIVO + linrodostat in MIBC. Here we describe a randomized, partially blinded, phase 3 study evaluating the efficacy and safety of NAC ± NIVO ± linrodostat followed by RC and continued IO tx in pts with MIBC (NCT03661320). Methods: Pts aged ≥ 18 years with previously untreated MIBC (clinical stage T2-T4a, N0, M0), creatinine clearance ≥ 50 mL/min, and predominant UC histology who are eligible for cisplatin-based NAC and RC will be enrolled. Pts with evidence of positive lymph node; metastatic BC; or prior systemic therapy, radiotherapy, or surgery for BC other than TURBT are not eligible. Pts will be randomized to receive NAC (gemcitabine/cisplatin; arm A), NAC + NIVO + oral placebo (arm B), or NAC + NIVO + linrodostat (arm C) followed by RC (all arms); arms B and C will receive continued IO tx. Primary endpoints include pCR after neoadjuvant tx and event-free survival (arms C vs A; arms B vs A). Secondary endpoints are overall survival and safety. This global study in 28 countries began accrual in Nov 2018 and has a target enrollment of 1200 pts. Clinical trial information: NCT03661320 .

Lung cancer immunochemotherapy: Codelivery of EGFR tki and PTX via an immunostimulatory dual functional nanocarrier.

e15177 Background: Immuno-target therapy combines a target therapy agent with an immune modulating agent and represents an attractive approach to improve cancer therapy.However, the success of it is hampered by the lack of a strategy to effectively co deliver the two therapeutics to the tumours.Here we report an improved dual functional nanocarrier (PEG5k-Fmoc-NLG2) to load Gefitinib for improved cancer Immuno target therapy.PEG5K-Fmoc-NLG2 is a prodrug that can inhibited IDO enzyme activity in vitro,while IDO1 inhibition reversed T cell suppression mediated by IDO expressing mouse cancer cells. Methods: Gefitinib loaded in carrier was prepared via a film hydrationmethod,the physicochemical properties of micelles was determined by TEM and particle size test.The cytotoxicity of the drug was detected by MTT assay. 3LL lung cancer was inoculated in mice and different drugs was injected through the tail vein to compare the anti tumor effect of drug loading micells with existing targeted drug gefitinib and CTLA4 antibody; tumor tissue proteins were extracted to clarify changes in pEGFR expressionexpression; flow cytometry will be finished to observe tumor immune microenvironment changes. Results: 1. Gefitinib loaded micelle maintain the similar size with blank PEG5k-fmoc-NLG2 micelles that is around 20nm.The drug-loaded micelles produced uniformed size and morphology. which further confirmed the size of micelles was around 20nm. 2. PTX and Gefitinib loaded in PEG5k-fmoc-NLG2 exhibited significantly enhanced tumor cell killing effect than the free drug on both A549 and 3LL cell lines. 3. The antitumor efficacy of different drugs loaded in the carrier were tested in a murine lung cancer model (3LL). All treatment showed significant better antitumor activity compared to the control group, Gefitinib/PEG5k-Fmoc-NLG2 plus CTLA4 antibody exhibited the best antitumor effect. Antitumor activity of gefitinib loaded in carrier was comparable with free gefitinib alone. 4. With various treatments the expression of p-EGFR protein level varied. Basically, compare with free gefitinib alone, the carrier loaded gefitinib was more effective in the inhibition of EGFR phosphorylation. Conclusions: We have shown that targeted delivery of PTX and Gefitinib via a immunostimulatory nanocarrier effectively improved drugs antitumor activity. More study about tumor immune microenvironment are required. Such strategy can be employed in novel therapy combining chemotherapy drugs and immunemodulating agents such as PD-1 and CTLA4.

Co-delivery of doxorubicin and epacadostat via heparin coated pH-sensitive liposomes to suppress the lung metastasis of melanoma.

High metastasis is responsible for the failure in the treatment of melanoma. Chemoimmunotherapy has shown conspicuous inhibition effects not only on the growth of tumor in situ, but also on the metastasis to distant organs. Given that the indoleamine-2,3 dioxygenase (IDO) overexpressed in the microenvironment of tumor leads to the immune escape, the combination of chemotherapeutic drug and IDO inhibitor might be a promising chemoimmunotherapy. Besides, the hematogenous metastasis mediated by platelets was supposed to be blocked by the heparin (HP). Therefore, a drug delivery system with all these elements involved might be a potential treatment for melanoma. Here, we developed a pH-sensitive liposomal dual-delivery system for doxorubicin (DOX) and epacadostat (EPA) with HP coated (HP/LDE). It was confirmed to enhance cytotoxicity and apoptosis, reverse the platelets-activated epithelial mesenchymal transformation (EMT) and prevent the invasion and migration in vitro. After systemic administration, HP/LDE provided the optimum anti-metastasis effect on the melanoma. The results of evaluation on DC maturation, CD8+ cytotoxic T lymphocytes (CTLs) activation and T cell mediated cytotoxicity were consistent in vitro and in vivo. Taken together, our study established a functional liposomal dual-delivery system with ideal anti-metastasis efficacy on melanoma.

Fish-oil supplementation decreases Indoleamine-2,3-Dioxygenase expression and increases hippocampal serotonin levels in the LPS depression model

AimTo test the hypothesis that the antidepressant-like effect of omega-3 polyunsaturated fatty acids is related to the Indoleamine-2,3-Dioxygenase (IDO) inhibition. MethodsAnimals were supplemented for 50 days with 3.0 g/kg of Fish Oil (FO) or received water (Control group – C), via gavage. At the end of this period, both groups were injected with LPS 24 h before the modified forced swim test (MFST) and the open field. To assess the possible involvement of IDO in the FO effects, we performed two independent experiments, using two IDO inhibitors: the direct inhibitor 1-methyl-DL-tryptophan (1-MT) and the anti-inflammatory drug minocycline (MINO), administered 23 h, 5 h and 1 h before the tests. After the tests, the animals’ hippocampi were removed for quantification of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) by HPLC, and for IDO expression by western blot. ResultsLPS induced a depressive-like state in the animals, and this effect was blocked by 1-MT, MINO and FO. Regardless of IDO inhibition, FO supplemented animals displayed an antidepressant-like response by increasing swimming and decreasing immobility frequencies in the MFST when compared to the control group. The immune challenge induced an over-expression of IDO and reduced hippocampal 5-HT levels, both of which were reversed by MINO and FO. ConclusionFO induced a pronounced antidepressant-like effect and prevented LPS-induced depressive-like behavior, and this effect was related to decreased IDO expression and increased 5-HT levels in the hippocampus.

Dysregulation at multiple points of the kynurenine pathway is a ubiquitous feature of renal cancer: implications for tumour immune evasion

BackgroundIndoleamine 2,3-dioxygenase (IDO), the first step in the kynurenine pathway (KP), is upregulated in some cancers and represents an attractive therapeutic target given its role in tumour immune evasion. However, the recent failure of an IDO inhibitor in a late phase trial raises questions about this strategy.MethodsMatched renal cell carcinoma (RCC) and normal kidney tissues were subject to proteomic profiling. Tissue immunohistochemistry and gene expression data were used to validate findings. Phenotypic effects of loss/gain of expression were examined in vitro.ResultsQuinolate phosphoribosyltransferase (QPRT), the final and rate-limiting enzyme in the KP, was identified as being downregulated in RCC. Loss of QPRT expression led to increased potential for anchorage-independent growth. Gene expression, mass spectrometry (clear cell and chromophobe RCC) and tissue immunohistochemistry (clear cell, papillary and chromophobe), confirmed loss or decreased expression of QPRT and showed downregulation of other KP enzymes, including kynurenine 3-monoxygenase (KMO) and 3-hydroxyanthranilate-3,4-dioxygenase (HAAO), with a concomitant maintenance or upregulation of nicotinamide phosphoribosyltransferase (NAMPT), the key enzyme in the NAD+ salvage pathway.ConclusionsWidespread dysregulation of the KP is common in RCC and is likely to contribute to tumour immune evasion, carrying implications for effective therapeutic targeting of this critical pathway

An albumin-bound drug conjugate of paclitaxel and indoleamine-2,3-dioxygenase inhibitor for enhanced cancer chemo-immunotherapy

Despite the promising target of immunosuppressive enzyme indoleamine-2,3-dioxygenase (IDO) for cancer immunotherapy, IDO blockade monotherapy does not show significant benefit to cancer patients in the clinic. Recent research has focused on the combinatorial therapy of the IDO inhibitor and the immune checkpoint blockade or chemotherapy. Here, we synthesize a drug conjugate methyltryptophan-paclitaxel (MP) by linking the IDO inhibitor, D-1-methyltryptophan (D-1MT), to the chemotherapeutic agent, paclitaxel (PTX), through an ester bond. MP exhibits a similar tubulin-stabilizing effect to PTX. Like PTX, MP binds to human serum albumin to form albumin-bound MP nanoparticles (MP NPs) with a particle size of ∼115 nm in diameter. MP NPs significantly improve the tumor concentration of D-1MT due to the hydrolysis of MP in tumors. The codelivery of PTX and D-1MT offered by MP NPs in tumors significantly enhances the anti-tumor effect compared with the albumin-bound PTX NPs. Immune cell phenotyping reveals that MP NPs ameliorate the immune environment through increasing the number of the effector CD8+ T cells, and decreasing the population of regulatory T cells and granulocyte-like myeloid-derived suppressor cells. These results prove that the design of the twin drug from the IDO inhibitor and PTX synergizes the anti-tumor effect and shows promise in clinical translation.

Cytokines differently define the immunomodulation of mesenchymal stem cells isolated from the periodontal ligament

Background & Aim Periodontal ligament derived mesenchymal stem cells (hPDLSCs) fulfil the minimal criteria of the International Society for Cellular Therapy (ISCT) for mesenchymal stem/stromal cells. In periodontal tissues these cells play a crucial role in tissue homeostasis and regeneration. The in vivo function of hPDLSCs is mainly executed by their immunomodulatory properties and is reciprocally affected by inflammatory cytokines which are secreted by immune cells. Such inflammatory cytokines are interferon (IFN)-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-1β, which trigger various signaling pathways and consequently may regulate immunomodulatory activities of hPDLSCs differently. The effect of these cytokines on hPDLSCs’ immunomodulation was not directly compared, so far. Methods, Results & Conclusion Hence, we directly compared in an indirect in vitro co-culture model the effect of IFN-γ, TNF-α or IL-1β treated primary hPDLSCs on CD4+ T lymphocyte proliferation. Further, the expression levels of the immunomodulatory factors indoleamine-2,3-dioxygenase-1 (IDO-1), programmed cell death 1 ligand 1 (PD-L1), programmed cell death 1 ligand 2 (PD-L2), TNF-inducible gene 6 protein (TSG-6) and prostaglandin E2 (PGE2) in cytokine treated hPDLSCs were directly compared. Additionally, IDO-1, PD-L1 and prostaglandin-endoperoxide synthase 2 (PTGS-2) were inhibited pharmacologically to compare their effects on CD4+ T lymphocyte proliferation under different cytokine conditions. CD4+ T lymphocyte proliferation was significantly decreased by hPDLSCs. This effect was intensified in the presence of IL-1β and IFN-γ but not by TNF-α. IFN-γ treated hPDLSCs showed a significantly stronger inhibition of CD4+ T lymphocyte proliferation than by IL-1β treated hPDLSCs. All three inflammatory cytokines showed significant different effects on the production of immunomodulatory factors in hPDLSCs. IDO-1, PD-L1 and PD-L2 expression levels were strongest increased by IFN-γ, PTGS-2 levels mainly by IL-1β and TSG-6 by IL-1β and TNF-α to a similar extent. Additionally, pharmacological inhibition of IDO-1, PD-L1 and PTGS-2 reversed the suppression of CD4+ T lymphocyte proliferation to different extent depending on the present cytokine. This study shows that cytokines variously activate immunomodulatory mechanisms of hPDLSCs probably due to boosting the production of different immunomodulatory factors. This may be involved in fine-tuning local inflammatory processes in periodontal tissues.

Programmed death ligand 1/indoleamine 2,3-dioxygenase 1 expression and tumor-infiltrating lymphocyte status in renal cell carcinoma with sarcomatoid changes and rhabdoid features

Renal cell carcinoma (RCC) with sarcomatoid changes and rhabdoid features has shown poor outcomes. Several immune checkpoint inhibitors including programmed cell death protein 1 (PD-1)/programmed death ligand-1 (PD-L1) inhibitors have been approved for the treatment of RCC. Combination therapy using PD-1/PD-L1 and indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors has also been used to treat various malignancies. However, little is known about IDO1 expression and therapeutic effects of the IDO1 inhibitor in RCC. Herein, we retrospectively analyzed the expression of PD-L1/IDO1 and examined its relationship with tumor-infiltrating lymphocyte (TIL) status and prognostic effect. We investigated the PD-L1, IDO1, CD3+, CD4+, and CD8+ immunoexpression status in 60 cases of sarcomatoid/rhabdoid RCC. The PD-L1 and IDO1 results were defined by the tumor proportion score. For the evaluation of TIL status, we counted the number of lymphocytes located in the tumor and averaged the numbers over five high-power fields for each case. The results revealed PD-L1 and IDO1 expression was observed more frequently in the sarcomatoid/rhabdoid component than in the nonsarcomatoid/nonrhabdoid component. The correlation between PD-L1 and IDO1 expression was significant (P=0.0076). PD-L1 expression and coexpression of PD-L1 and IDO1 were correlated with a high density of CD3+, CD4+, and CD8+ T cells. There was no significant difference in overall survival among the patients with PD-L1 and/or IDO1 expression, but PD-L1 expression and coexpression were related to poor progression-free survival. Our results suggest that combination therapy using the PD-1/PD-L1 inhibitor and IDO1 inhibitor may be effective for treating sarcomatoid/rhabdoid RCC.

Identification of potential indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitors by an FBG-based 3D QSAR pharmacophore model

As a rate-limiting enzyme in the major pathway of l-tryptophan catabolism, indoleamine 2, 3-dioxygenase 1 (IDO1) has been regarded as a potential target for the treatment of a variety of diseases. To identify the key molecular features and extend the structural variety of IDO1 inhibitors, a ferrous binding group (FBG)-based 3D-QSAR pharmacophore model was constructed, validated and used for virtual screening herein. The Specs database was initially filtered based on drug-like rules, and was subsequently screened by the pharmacophore model. Molecular docking simulations and similarity analysis were then followed to prioritize twenty compounds for biological tests. Among them, compound VS-13 exhibited moderate inhibitory activity against IDO1, and could be subjected to further structure-activity relationship studies and structural optimization.

Kynurenine pathway enzyme KMO in cancer progression: A tip of the Iceberg

Kynurenine pathway enzyme KMO in cancer progression: A tip of the Iceberg

Interferon-Induced IDO1 Mediates Radiation Resistance and Is a Therapeutic Target in Colorectal Cancer.

Colorectal cancer is a major cause of mortality worldwide. Chemotherapy and radiation remain standard treatment for locally advanced disease, with current immune-targeting therapies applying to only a small subset of patients. Expression of the immuno-oncology target indoleamine 2,3 dioxygenase 1 (IDO1) is associated with poor colorectal cancer clinical outcomes but is understudied as a potential treatment target. In this study, we examined the interaction between the IDO1 pathway and radiotherapy in colorectal cancer. We used human and mouse colorectal cancer cell lines, organoids, mouse syngeneic colorectal cancer tumor graft models, and colorectal cancer tissues from patients who received radiotherapy. IDO1 activity was blocked using the clinical IDO1 inhibitor epacadostat and by genetic disruption. We found that radiation induced IDO1 overexpression in colorectal cancer through type I and II IFN signaling. IDO1 enzymatic activity directly influenced colorectal cancer radiation sensitivity. IDO1 inhibition sensitized colorectal cancer to radiation-induced cell death, whereas the IDO1 metabolite kynurenine promoted radioprotection. IDO1 inhibition also potentiated Th1 cytokines and myeloid cell-modulating factors in the tumor microenvironment and promoted an abscopal effect on tumors outside the radiation field. Conversely, IDO1 blockade protected the normal small intestinal epithelium from radiation toxicity and accelerated recovery from radiation-induced weight loss, indicating a role in limiting side effects. These data demonstrated that IDO1 inhibition potentiates radiotherapy effectiveness in colorectal cancer. The findings also provide rationale and mechanistic insight for the study of IDO1 inhibitors as adjuvant therapy to radiation in patients with locally advanced sporadic and colitis-associated colorectal cancer.