Indoleamine 2,3-dioxygenase: is it an immune suppressor?

The role of tryptophan metabolism and tolerogenic dendritic cells in maintaining immune tolerance: Insights into celiac disease pathogenesis

BACKGROUND

In mammals, amino acid metabolism has evolved to control immune responses. Tryptophan (Trp) is the rarest essential amino acid found in food and its metabolism has evolved to be a primary regulatory node in the control of immune responses. Celiac disease (CeD) is a developed immunological condition caused by gluten intolerance and is linked to chronic small intestine enteropathy in genetically predisposed individuals. Dendritic cells (DCs), serving as the bridge between innate and adaptive immunities, can influence immunological responses in CeD through phenotypic alterations.

OBJECTIVE

This review aims to highlight the connection between Trp metabolism and tolerogenic DCs, and the significance of this interaction in the pathogenesis of CeD.

RESULTS

It is been recognized that various DC subtypes contribute to the pathogenesis of CeD. Tolerogenic DCs, in particular, are instrumental in inducing immune tolerance, leading to T-reg differentiation that helps maintain intestinal immune tolerance against inflammatory responses in CeD patients and those with other autoimmune disorders. T-regs, a subset of T-cells, play a crucial role in maintaining intestinal immunological homeostasis by regulating the activities of other immune cells. Notably, Trp metabolism, essential for T-reg function, facilitates T-reg differentiation through microbiota-mediated degradation and the kynurenine pathway.

CONCLUSION

Therefore, alterations in Trp metabolism could potentially influence the immune response in CeD, affecting both the development of the disease and the persistence of symptoms despite adherence to a gluten-free diet.

Biochemical hallmarks-targeting antineoplastic nanotherapeutics

Tumor microenvironments (TMEs) have received increasing attention in recent years as they play pivotal roles in tumorigenesis, progression, metastases, and resistance to the traditional modalities of cancer therapy like chemotherapy. With the rapid development of nanotechnology, effective antineoplastic nanotherapeutics targeting the aberrant hallmarks of TMEs have been proposed. The appropriate design and fabrication endow nanomedicines with the abilities for active targeting, TMEs-responsiveness, and optimization of physicochemical properties of tumors, thereby overcoming transport barriers and significantly improving antineoplastic therapeutic benefits. This review begins with the origins and characteristics of TMEs and discusses the latest strategies for modulating the TMEs by focusing on the regulation of biochemical microenvironments, such as tumor acidosis, hypoxia, and dysregulated metabolism. Finally, this review summarizes the challenges in the development of smart anti-cancer nanotherapeutics for TME modulation and examines the promising strategies for combination therapies with traditional treatments for further clinical translation.

Corilagin alleviates liver fibrosis in zebrafish and mice by repressing IDO1-mediated M2 macrophage repolarization

BACKGROUND

Liver fibrosis caused by chronic liver injury, eventually develops into liver cirrhosis and hepatocellular carcinoma. Currently, there are no effective drugs to relieve liver fibrosis due to the lack of molecular pathogenesis characteristics. Former research demonstrates that the hepatic immune microenvironment plays a key role in the pathogenesis of liver fibrosis, thus macrophages are important immune cells in the liver. Our previous study has found that IDO1 plays an important role in the liver immune microenvironment. CRG is a gallic acid tannin found in medicinal plants of many ethnicities that protects against inflammation, tumors and chronic liver disease. However, the mechanism of by which CRG mediates the interaction of IDO1 with macrophages during hepatic immune maturation is not clear.

PURPOSE

To investigate the regulatory mechanism of CRG in liver fibrosis and the intrinsic relationship between IDO1 and macrophage differentiation.

METHODS

Zebrafish, RAW264.7 cells and mice were used in the study. IDO1 overexpression and knockdown cell lines were constructed using lentiviral techniques.

RESULTS

We discovered that CRG remarkably reduced the AST and ALT serum levels. Histological examination revealed that CRG ameliorates CCL4-induced liver fibrosis and depressed the expression of α-SMA, Lamimin, Collagen-Ι and fibronectin. Besides, we found that CRG promoted increased MerTK expression on partly macrophages. Interestingly, in vitro, we found that CRG suppressed IDO1 expression and regulated macrophage differentiation by upregulating CD86, CD80 and iNOS, while downregulating CD206, CD163, IL-4 and IL-10 expression. Additionally, we found that CRG could inhibit hepatic stellate cell activation by direct or indirect action.

CONCLUSION

Our findings suggest that CRG alleviates liver fibrosis by mediating IDO1-mediated M2 macrophage repolarization.

Druggable targets for the immunopathy of Alzheimer's disease

Alzheimer's disease (AD) is one of the leading threats to the health and socioeconomic well-being of humankind. Though research to develop disease modifying therapies for AD has traditionally focussed on the misfolding and aggregation of proteins, this approach has failed to yield a definitively curative agent. Accordingly, the search for additional or alternative approaches is a medicinal chemistry priority. Dysfunction of the brain's neuroimmune-neuroinflammation axis has emerged as a leading contender. Neuroimmunity however is mechanistically complex, rendering the recognition of candidate receptors a challenging task. Herein, a review of the role of neuroimmunity in the biomolecular pathogenesis of AD is presented with the identification of a 'druggable dozen' targets; in turn, each identified target represents one or more discrete receptors centred on a common biochemical mechanism. The druggable dozen is composed of both cellular and molecular messenger targets, with a 'targetable ten' microglial targets as well as two cytokine-based targets. For each target, the underlying molecular basis, with a consideration of strengths and weaknesses, is considered.

Intra-articular delivery of an indoleamine 2,3-dioxygenase galectin-3 fusion protein for osteoarthritis treatment in male Lewis rats

OBJECTIVE

Osteoarthritis (OA) is driven by low-grade inflammation, and controlling local inflammation may offer symptomatic relief. Here, we developed an indoleamine 2,3-dioxygenase and galectin-3 fusion protein (IDO-Gal3), where IDO increases the production of local anti-inflammatory metabolites and Gal3 binds carbohydrates to extend IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA.

METHODS

Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT + MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n = 8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3s's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT + MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n = 7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed.

RESULTS

The Gal3 fusion increased joint residence in OA and contralateral knees (p < 0.0001). In OA-affected animals, both saline and IDO-Gal3 improved tactile sensitivity (p = 0.008), but IDO-Gal3 also increased walking velocities (p ≤ 0.033) and improved vertical ground reaction forces (p ≤ 0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p = 0.0025).

CONCLUSION

Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.

Unlocking therapeutic potential: integration of drug repurposing and immunotherapy for various disease targeting

Drug repurposing, also known as drug repositioning, entails the application of pre-approved or formerly assessed drugs having potentially functional therapeutic amalgams for curing various disorders or disease conditions distinctive from their original remedial indication. It has surfaced as a substitute for the development of drugs for treating cancer, cardiovascular diseases, neurodegenerative disorders, and various infectious diseases like Covid-19. Although the earlier lines of findings in this area were serendipitous, recent advancements are based on patient centered approaches following systematic, translational, drug targeting practices that explore pathophysiological ailment mechanisms. The presence of definite information and numerous records with respect to beneficial properties, harmfulness, and pharmacologic characteristics of repurposed drugs increase the chances of approval in the clinical trial stages. The last few years have showcased the successful emergence of repurposed drug immunotherapy in treating various diseases. In this light, the present review emphasises on incorporation of drug repositioning with Immunotherapy targeted for several disorders.

Lipopolysaccharide-Induced Delirium-like Behaviour in a Rat Model of Chronic Cerebral Hypoperfusion Is Associated with Increased Indoleamine 2,3-Dioxygenase Expression and Endotoxin Tolerance

Indoleamine 2,3-dioxygenase (IDO) and the tryptophan-kynurenine pathway (TRP-KP) are upregulated in ageing and could be implicated in the pathogenesis of delirium. This study evaluated the role of IDO/KP in lipopolysaccharide (LPS)-induced delirium in an animal model of chronic cerebral hypoperfusion (CCH), a proposed model for delirium. CCH was induced by a permanent bilateral common carotid artery ligation (BCCAL) in Sprague Dawley rats to trigger chronic neuroinflammation-induced neurodegeneration. Eight weeks after permanent BCCAL, the rats were treated with a single systemic LPS. The rats were divided into three groups: (1) post-BCCAL rats treated with intraperitoneal (i.p.) saline, (2) post-BCCAL rats treated with i.p. LPS 100 μg/kg, and (3) sham-operated rats treated with i.p. LPS 100 μg/kg. Each group consisted of 10 male rats. To elucidate the LPS-induced delirium-like behaviour, natural and learned behaviour changes were assessed by a buried food test (BFT), open field test (OFT), and Y-maze test at 0, 24-, 48-, and 72 h after LPS treatment. Serum was collected after each session of behavioural assessment. The rats were euthanised after the last serum collection, and the hippocampi and cerebral cortex were collected. The TRP-KP neuroactive metabolites were measured in both serum and brain tissues using ELISA. Our data show that LPS treatment in CCH rats was associated with acute, transient, and fluctuated deficits in natural and learned behaviour, consistent with features of delirium. These behaviour deficits were mild compared to the sham-operated rats, which exhibited robust behaviour impairments. Additionally, heightened hippocampal IDO expression in the LPS-treated CCH rats was associated with reduced serum KP activity together with a decrease in the hippocampal quinolinic acid (QA) expression compared to the sham-operated rats, suggested for the presence of endotoxin tolerance through the immunomodulatory activity of IDO in the brain. These data provide new insight into the underlying mechanisms of delirium, and future studies should further explore the role of IDO modulation and its therapeutic potential in delirium.

Indoleamine-2,3 dioxygenase: a fate-changer of the tumor microenvironment

Indoleamine-2,3 dioxygenase is a rate-limiting enzyme in the tryptophan catabolism in kynurenine pathways that has an immunosuppressive effect and supports cancer cells to evade the immune system in different cancer types. Diverse cytokines and pathways upregulate the production of indoleamine-2,3 dioxygenase enzymes in the tumor microenvironment and cause more production and activity of this enzyme. Ultimately, this situation results in anti-tumor immune suppression which is in favor of tumor growth. Several inhibitors such as 1-methyl-tryptophan have been introduced for indoleamine-2,3 dioxygenase enzyme and some of them are widely utilized in pre-clinical and clinical trials. Importantly at the molecular level, indoleamine-2,3 dioxygenase is positioned in a series of intricate signaling and molecular networks. Here, the main objective is to provide a focused view of indoleamine-2,3 dioxygenase enhancer pathways and propose further studies to cover the gap in available information on the function of indoleamine-2,3 dioxygenase enzyme in the tumor microenvironment.

Intra-Articular Delivery of an Indoleamine 2,3-Dioxygenase Galectin-3 Fusion Protein for Osteoarthritis Treatment in Male Lewis Rats

Objective : Controlling joint inflammation can improve osteoarthritis (OA) symptoms; however, current treatments often fail to provide long-term effects. We have developed an indoleamine 2,3-dioxygenase and galectin-3 fusion protein (IDO-Gal3). IDO converts tryptophan to kynurenines, directing the local environment toward an anti-inflammatory state; Gal3 binds carbohydrates and extends IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA. Methods : Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT+MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n=8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT+MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n=7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed. Results : The Gal3 fusion increased joint residence in OA and contralateral knees (p<0.0001). In OA-affected animals, IDO-Gal3 improved tactile sensitivity (p=0.002), increased walking velocities (p≤0.033), and improved vertical ground reaction forces (p≤0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p=0.0025). Conclusion : Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.

GSDMD-mediated pyroptosis restrains intracellular Chlamydia trachomatis growth in macrophages

Pyroptosis, a type of programmed necrosis associated with inflammatory, is a host defense mechanism against microbial infections. Although Chlamydia has been shown to induce pyroptosis, whether pyroptosis directly impacts the growth of Chlamydia has not been demonstrated. In this study, we found that C. trachomatis L2 infection of the mouse macrophage RAW 264.7 cells induced pyroptosis by monitoring the ultrastructural changes under transmission electron microscopy and the release of LDH and IL-1β. More importantly, this C. trachomatis-triggered pyroptosis with activation of caspase-1 and caspase-11 was also accompanied by gasdermin D (GSDMD) activation. Suppression of these two inflammatory caspases inhibited GSDMD activation. Interestingly, the C. trachomatis-triggered pyroptosis significantly inhibited the intracellular growth of C. trachomatis since inactivation of either GSDMD or caspase-1/11 significantly rescued infectious C. trachomatis yields, which suggests pyroptosis response can be utilized as an intrinsic mechanism to restrict C. trachomatis intracellular infection in addition to the well- documented extrinsic mechanisms by recruiting and enhancing inflammatory responses. This study may reveal novel targets for attenuating C. trachomatis infectivity and/or pathogenicity.

TIGIT signaling and its influence on T cell metabolism and immune cell function in the tumor microenvironment

One of the key challenges for successful cancer therapy is the capacity of tumors to evade immune surveillance. Tumor immune evasion can be accomplished through the induction of T cell exhaustion via the activation of various immune checkpoint molecules. The most prominent examples of immune checkpoints are PD-1 and CTLA-4. Meanwhile, several other immune checkpoint molecules have since been identified. One of these is the T cell immunoglobulin and ITIM domain (TIGIT), which was first described in 2009. Interestingly, many studies have established a synergistic reciprocity between TIGIT and PD-1. TIGIT has also been described to interfere with the energy metabolism of T cells and thereby affect adaptive anti-tumor immunity. In this context, recent studies have reported a link between TIGIT and the hypoxia-inducible factor 1-α (HIF1-α), a master transcription factor sensing hypoxia in several tissues including tumors that among others regulates the expression of metabolically relevant genes. Furthermore, distinct cancer types were shown to inhibit glucose uptake and effector function by inducing TIGIT expression in CD8+ T cells, resulting in an impaired anti-tumor immunity. In addition, TIGIT was associated with adenosine receptor signaling in T cells and the kynurenine pathway in tumor cells, both altering the tumor microenvironment and T cell-mediated immunity against tumors. Here, we review the most recent literature on the reciprocal interaction of TIGIT and T cell metabolism and specifically how TIGIT affects anti-tumor immunity. We believe understanding this interaction may pave the way for improved immunotherapy to treat cancer.

Necroptosis and Alzheimer's Disease: Pathogenic Mechanisms and Therapeutic Opportunities

Alzheimer's disease (AD) is considered to be the most common neurodegenerative disease, with clinical symptoms encompassing progressive memory loss and cognitive impairment. Necroptosis is a form of programmed necrosis that promotes cell death and neuroinflammation, which further mediates the pathogenesis of several neurodegenerative diseases, especially AD. Current evidence has strongly suggested that necroptosis is activated in AD brains, resulting in neuronal death and cognitive impairment. We searched the PubMed database, screening all articles published before September 28, 2022 related to necroptosis in the context of AD pathology. The keywords in the search included: "necroptosis", "Alzheimer's disease", "signaling pathways", "Aβ", Aβo", "Tau", "p-Tau", "neuronal death", "BBB damage", "neuroinflammation", "microglia", "mitochondrial dysfunction", "granulovacuolar degeneration", "synaptic loss", "axonal degeneration", "Nec-1", "Nec-1s", "GSK872", "NSA", "OGA", "RIPK1", "RIPK3", and "MLKL". Results show that necroptosis has been involved in multiple pathological processes of AD, including amyloid-β aggregation, Tau accumulation, neuronal death, and blood-brain barrier damage, etc. More importantly, existing research on AD necroptosis interventions, including drug intervention and potential gene targets, as well as its current clinical development status, was discussed. Finally, the issues pertaining to necroptosis in AD were presented. Accordingly, this review may provide further insight into clinical perspectives and challenges for the future treatment of AD by targeting the necroptosis pathway.

Activities of plasma indoleamine-2, 3-dioxygenase (IDO) enzyme in Nigerian patients with lung diseases: basis for tryptophan supplementation or IDO inhibitor use

Background

Clinical trial of IDO inhibitor or uses of micro-nutrient supplements during management of diseases is commonly done without having adequate basis for the practise. Tryptophan (Trp) is an essential amino acid needed for T-lymphocyte function, and indoleamine-2,3-dioxygenase (IDO) is a potent immunoregulatory molecule that catalyses the rate-limiting step of Trp degradation in the kynurenine (Kyn) pathway.

Materials and methods

Human IDO in the plasma samples was measured using ELISA in patients with non-infectious (asthma) and infectious diseases (pulmonary tuberculosis and COVID-19) compared with corresponding un-infected controls.

Results

Mean IDO activity in COVID-19 patients was significantly higher compared with corresponding control (p = 0.001) while mean IDO activity in pulmonary tuberculosis patients was non-significantly higher compared with corresponding control (p = 0.520), and mean IDO activity in asthma patients was non-significantly lower compared with corresponding control (p = 0.102).

Conclusion

Our data suggest that IDO activity as an innate immune factor is increased in infectious lung diseases (COVID-19 and pulmonary tuberculosis) but reduced in non-infectious disease (asthma) and that use of tryptophan supplementation or IDO inhibitor may not be necessary in all lung diseases.

The role behind the scenes of Tregs and Th17s in Hashimoto's thyroiditis: Toward a pivotal role of FOXP3 and BACH2

In Hashimoto's thyroiditis (HT), the genetic bases play a central role in determining development of the disease. In particular, the most frequent genes involved in the onset of HT are the Human Leukocyte Antigen (HLA). However, there are other genes and transcription factors in the autoimmune background of HT, both isolated and as part of autoimmune polyendocrine syndromes (APS). Recently more interest is being fueled toward BACH2 (BTB Domain and CNC Homolog 2), that promotes Tregs (T regulators lymphocytes) differentiation and enhances Treg-mediated immunity. The synergistic interaction between environmental agents and the aforementioned genes leads to the onset of autoimmunity and ultimately to damage of the thyroid gland. In this scenario, the role of Th17 (T helper-17 lymphocytes) and Treg cells is still less defined as compared to action of Th1 cells (T helper-1 lymphocytes) and cytotoxic lymphocytes (CD8 ⁺ T lymphocytes). Evidences show that an imbalance of Th17/Treg ratio represents a prognostic factor with respect to the gland damage. Moreover, the deficient ability of Treg to inhibit the proliferation of T cells against the self can break the immune balance. In light of these considerations, the use of genetic panels and the progress of immunotherapy could allow for better targeting treatment and preventive interventions in subjects with potential or early stage of HT.

A Fresh Glimpse into Cartilage Immune Privilege

The increasing prevalence of degenerative cartilage disorders in young patients is a growing public concern worldwide. Cartilage's poor innate regenerative capacity has inspired the exploration and development of cartilage replacement treatments such as tissue-engineered cartilages and osteochondral implants as potential solutions to cartilage loss. The clinical application of tissue-engineered implants is hindered by the lack of long-term follow-up demonstrating efficacy, biocompatibility, and bio-integration. The historically reported immunological privilege of cartilage tissue was based on histomorphological observations pointing out the lack of vascularity and the presence of a tight extracellular matrix. However, clinical studies in humans and animals do not unequivocally support the immune-privilege theory. More in-depth studies on cartilage immunology are needed to make clinical advances such as tissue engineering more applicable. This review analyzes the literature that supports and opposes the concept that cartilage is an immune-privileged tissue and provides insight into mechanisms conferring various degrees of immune privilege to other, more in-depth studied tissues such as testis, eyes, brain, and cancer.

Indoleamine 2,3-Dioxygenase Immune Status as a Potential Biomarker of Radioiodine Efficacy for Advanced Distant Metastatic Differentiated Thyroid Cancer

Purpose

Host immunity influences the impact of cancer therapy but the effect of immune status in radioiodine (RAI)-treated differentiated thyroid cancer (DTC) remains obscure. Here we investigated indoleamine 2,3-dioxygenase (IDO) activity as a biomarker of response to RAI in patients with distant metastatic DTC (dmDTC).

Methods

Patients with dmDTC receiving RAI were evaluated for serum IDO activity (kynurenine and kynurenine:tryptophan ratio) at baseline and 3 months after RAI. The optimal cut-off value for these biomarkers to predict response was established by receiver operating characteristic analysis. The relationship between disease outcomes, overall survival (OS) and progression-free survival (PFS), and IDO activity levels was studied.

Results

Higher baseline kynurenine:tryptophan ratio (&gt;2.46) was correlated with poorer RAI response as well as shorter median PFS (45 mo versus not reached, p=0.002) and OS (78 mo versus not reached, p=0.035). High baseline kynurenine:tryptophan ratio was also correlated with a reduced number of tumor-infiltrating lymphocytes. Higher post/pre-kynurenine ratio (&gt;1.69) was associated with survival endpoints: shorter median PFS (48 mo versus not reached, p=0.002) and OS (68 mo versus not reached, p=0.010). Favorable baseline and favorable change corresponded with better PFS and OS.

Conclusions

Our results suggest that RAI also alters IDO activity in dmDTC patients. IDO activity could predict progression and survival outcomes for advanced dmDTC patients. Serum IDO biomarker levels could be used to select dmDTC likely to benefit from RAI therapy, although further studies are necessary.

Quantification of Linrodostat and its metabolites: Overcoming bioanalytical challenges in support of a discovery Indoleamine 2,3 dioxygenase program

BMS-986205 (Linrodostat) is a small molecule inhibitor of Indoleamine 2, 3 dioxygenase (IDO) that is currently being evaluated in clinical trials for the oral treatment of advanced cancer. Initially, there were concerns regarding possible toxicity following administration, since BMS-986205 undergoes metabolism to form 4-chloroaniline. However, it was later determined that the downstream metabolites of 4-chloroaniline might be a greater concern. To evaluate the potential toxicity of these metabolites, a sensitive LC-MS/MS analytical method was needed to quantify both the parent compound and multiple metabolites. This presented a challenge since the method required the analysis of multiple analytes while still retaining the analytical sensitivity required to support studies. By utilizing a multi-function analytical method, we were able to quantify the necessary analytes using a complex LC-MS/MS-based method including the application of both negative and positive electrospray ionization.

The Immunomodulatory Enzyme IDO2 Mediates Autoimmune Arthritis through a Nonenzymatic Mechanism

IDO2 is one of two closely related tryptophan catabolizing enzymes induced under inflammatory conditions. In contrast to the immunoregulatory role defined for IDO1 in cancer models, IDO2 has a proinflammatory function in models of autoimmunity and contact hypersensitivity. In humans, two common single-nucleotide polymorphisms have been identified that severely impair IDO2 enzymatic function, such that <25% of individuals express IDO2 with full catalytic potential. This, together with IDO2's relatively weak enzymatic activity, suggests that IDO2 may have a role outside of its function in tryptophan catabolism. To determine whether the enzymatic activity of IDO2 is required for its proinflammatory function, we used newly generated catalytically inactive IDO2 knock-in mice together with established models of contact hypersensitivity and autoimmune arthritis. Contact hypersensitivity was attenuated in catalytically inactive IDO2 knock-in mice. In contrast, induction of autoimmune arthritis was unaffected by the absence of IDO2 enzymatic activity. In pursuing this nonenzymatic IDO2 function, we identified GAPDH, Runx1, RANbp10, and Mgea5 as IDO2-binding proteins that do not interact with IDO1, implicating them as potential mediators of IDO2-specific function. Taken together, our findings identify a novel function for IDO2, independent of its tryptophan catabolizing activity, and suggest that this nonenzymatic function could involve multiple signaling pathways. These data show that the enzymatic activity of IDO2 is required only for some inflammatory immune responses and provide, to our knowledge, the first evidence of a nonenzymatic role for IDO2 in mediating autoimmune disease.

Immunogenic Cell Death in Cancer Therapy

Apoptosis plays a crucial role in chemotherapy-induced cell death. The conventional theory holding that apoptosis needs to be immunologically silent has recently been revised, and the concept of immunogenic cell death (ICD) has been proposed. This review describes the main features of ICD induction. These ICD markers are important for the effectiveness of anticancer therapy, as well as for basic research into cell death regulation. The mechanism of the "vaccination effect" of dying cancer cells undergoing ICD has been fully described, including the activation of specific antitumor response after re-challenge by the same living tumor cells. This review also discusses the whole set of molecular events attributing cell death to immunogenic type: the exposure of calreticulin and the heat shock protein HSP70 to the outer surface of the cell membrane and the release of the nuclear protein HMGB1 and ATP into the extracellular space. ICD inducers of various nature (chemotherapy drugs, cytotoxic proteins, and oncolytic viruses), as well as physical methods, are classified in the current review.

Molecular Targets of Natural Compounds with Anti-Cancer Properties

Cancer is the second leading cause of death in humans. Despite rapid developments in diagnostic methods and therapies, metastasis and resistance to administrated drugs are the main obstacles to successful treatment. Therefore, the main challenge should be the diagnosis and design of optimal therapeutic strategies for patients to increase their chances of responding positively to treatment and increase their life expectancy. In many types of cancer, a deregulation of multiple pathways has been found. This includes disturbances in cellular metabolism, cell cycle, apoptosis, angiogenesis, or epigenetic modifications. Additionally, signals received from the microenvironment may significantly contribute to cancer development. Chemical agents obtained from natural sources seem to be very attractive alternatives to synthetic compounds. They can exhibit similar anti-cancer potential, usually with reduced side effects. It was reported that natural compounds obtained from fruits and vegetables, e.g., polyphenols, flavonoids, stilbenes, carotenoids and acetogenins, might be effective against cancer cells in vitro and in vivo. Several published results indicate the activity of natural compounds on protein expression by its influence on transcription factors. They could also be involved in alterations in cellular response, cell signaling and epigenetic modifications. Such natural components could be used in our diet for anti-cancer protection. In this review, the activities of natural compounds, including anti-cancer properties, are described. The influence of natural agents on cancer cell metabolism, proliferation, signal transduction and epigenetic modifications is highlighted.

Hypoxia and the Kynurenine Pathway: Implications and Therapeutic Prospects in Alzheimer's Disease

Neurodegenerative diseases (NDs) like Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease predominantly pose a significant socioeconomic burden. Characterized by progressive neural dysfunction coupled with motor or intellectual impairment, the pathogenesis of ND may result from contributions of certain environmental and molecular factors. One such condition is hypoxia, characterized by reduced organ/tissue exposure to oxygen. Reduced oxygen supply often occurs during the pathogenesis of ND and the aging process. Despite the well-established relationship between these two conditions (i.e., hypoxia and ND), the underlying molecular events or mechanisms connecting hypoxia to ND remain ill-defined. However, the relatedness may stem from the protective or deleterious effects of the transcription factor, hypoxia-inducible factor 1-alpha (HIF-1α). The upregulation of HIF-1α occurs in the pathogenesis of most NDs. The dual function of HIF-1α in acting as a "killer factor" or a "protective factor" depends on the prevailing local cellular condition. The kynurenine pathway is a metabolic pathway involved in the oxidative breakdown of tryptophan. It is essential in neurotransmission and immune function and, like hypoxia, associated with ND. Thus, a good understanding of factors, including hypoxia (i.e., the biochemical implication of HIF-1α) and kynurenine pathway activation in NDs, focusing on Alzheimer's disease could prove beneficial to new therapeutic approaches for this disease, thus the aim of this review.

Kynurenine pathway activation and deviation to anthranilic and kynurenic acid in fibrosing chronic graft-versus-host disease

Fibrosing chronic graft-versus-host disease (cGVHD) is a debilitating complication of allogeneic stem cell transplantation (alloSCT). A driver of fibrosis is the kynurenine (Kyn) pathway, and Kyn metabolism patterns and cytokines may influence cGVHD severity and manifestation (fibrosing versus gastrointestinal [GI] cGVHD). Using a liquid chromatography-tandem mass spectrometry approach on sera obtained from 425 patients with allografts, we identified high CXCL9, high indoleamine-2,3-dioxygenase (IDO) activity, and an activated Kyn pathway as common characteristics in all cGVHD subtypes. Specific Kyn metabolism patterns could be identified for non-severe cGVHD, severe GI cGVHD, and fibrosing cGVHD, respectively. Specifically, fibrosing cGVHD was associated with a distinct pathway shift toward anthranilic and kynurenic acid, correlating with reduced activity of the vitamin-B2-dependent kynurenine monooxygenase, low vitamin B6, and increased interleukin-18. The Kyn metabolite signature is a candidate biomarker for severe fibrosing cGVHD and provides a rationale for translational trials on prophylactic vitamin B2/B6 supplementation for cGVHD prevention.

High IDO activity and an activated Kyn pathway are common in all cGVHD subtypes

Specific Kyn metabolism patterns were identified for gastrointestinal and fibrosing cGVHD

A pathway shift toward anthranilic and kynurenic acid was found in fibrosing cGVHD

A rationale for vitamin B2/B6 adjustment for cGVHD prevention is presented

Tryptophan potentiates CD8+ T cells against cancer cells by TRIP12 tryptophanylation and surface PD-1 downregulation

BACKGROUND

Tryptophan catabolites suppress immunity. Therefore, blocking tryptophan catabolism with indoleamine 2,3-dioxygenase (IDO) inhibitors is pursued as an anticancer strategy.

METHODS

The intracellular level of tryptophan and kynurenine was detected by mass spectrum analysis. The effect of tryptophan and IDO inhibitors on cell surface programmed cell death protein 1 (PD-1) level were measured by flow cytometry. A set of biochemical analyses were used to figure out the underlying mechanism. In vitro co-culture system, syngeneic mouse models, immunofluorescent staining, and flow cytometry analysis were employed to investigate the role of tryptophan and IDO inhibitor in regulating the cytotoxicity of CD8⁺ T cells.

RESULTS

Here, we reported that IDO inhibitors activated CD8⁺ T cells also by accumulating tryptophan that downregulated PD-1. Tryptophan and IDO inhibitors administration, both increased intracellular tryptophan, and tryptophanyl-tRNA synthetase (WARS) overexpression decreased Jurkat and mice CD8⁺ T cell surface PD-1. Mechanistically, WARS tryptophanylated lysine 1136 of and activated E3 ligase TRIP12 to degrade NFATc1, a PD-1 transcription activator. SIRT1 de-tryptophanylated TRIP12 and reversed the effects of tryptophan and WARS on PD-1. Tryptophan or IDO inhibitors potentiated CD8⁺ T cells to induce apoptosis of co-cultured cancer cells, increased cancer-infiltrating CD8⁺ T cells and slowed down tumor growth of lung cancer in mice.

CONCLUSIONS

Our results revealed the immune-activating efficacy of tryptophan, and suggested tryptophan supplemental may benefit IDO inhibitors and PD-1 blockade during anticancer treatments.

Nanomolar potency of imidazo[2,1-b]thiazole analogs as indoleamine 2,3-dioxygenase inhibitors

Novel series of imidazo[2,1-b]thiazole analogs were designed, synthesized, and biologically evaluated as indoleamine 2,3-dioxygenase (IDO1) inhibitors. Imidazo[2,1-b]thiazoles 6, 7, and 8 showed inhibitory profiles against IDO1 at IC₅₀ values of 68.48, 82.39, and 48.48 nM, respectively, compared with IDO5L at IC₅₀ 67.40 nM. Benzo[d]imidazo[2,1-b]thiazoles 17, 20, and 22 showed promising IDO1 inhibition at IC₅₀ values of 53.58, 53.16, and 57.95 nM, respectively. Compound 7 showed a growth-inhibitory profile at GI of 39.33% against the MCF7 breast cancer cell line, while 8 proved lethal to ACHN renal cancer cells. Cells treated with compounds 17 and 22 showed a typical apoptosis pattern of DNA fragments that reflected the G0/G1, S, and G2/M phases of the cell cycle, together with a pre-G1 phase corresponding to apoptotic cells, which indicates that cell growth arrest occurred at the S phase. Molecular modeling simulations validated the potential of benzo[d]imidazo[2,1-b]thiazole analogs to chelate iron(III) within the IDO1 binding pocket and, hence, to have a better binding affinity via hydrophobic-hydrophobic interactions.

Prognostic impact of indoleamine 2,3-dioxygenase 1 (IDO1) mRNA expression on circulating tumour cells of patients with head and neck squamous cell carcinoma

Background

We sought to determine the prognostic role of indoleamine 2,3-dioxygenase 1 (IDO1) by evaluating IDO1 expression in circulating tumour cells (CTCs) at baseline and after completion of chemoradiotherapy in patients with locally advanced (LA) head and neck squamous cell carcinoma (HNSCC) treated with curative intent.

Methods

In a prospective cohort of 113 patients with LA HNSCC, we evaluated expression of IDO1 in the EpCAM+ CTC fraction at baseline and after cisplatin chemoradiation. The prognostic value of combined programmed cell death ligand-1 (PDL-1) and IDO1 expression was assessed.

Results

IDO1 was significantly overexpressed at baseline compared with the post-treatment counterparts (p=0.007). IDO1 messenger RNA (mRNA) expression at baseline was associated with better survival in terms of progression-free survival (PFS) (HR=0.19, p=0.017). Post-treatment IDO1 mRNA levels were correlated with unfavourable prognosis in terms of overall survival (OS) (HR=3.27, p=0.008). Patients with combined decreased expression levels of PDL-1 and IDO1 after treatment exhibited superior PFS (p=0.043) and OS (p=0.021).

Conclusions

Our results strongly suggest that IDO1 mRNA expression is an independent prognostic factor for clinical outcome. Our study provides useful information for future trials combining chemoradiation with immune checkpoint inhibitors and IDO1 inhibitors.

Checkpoint inhibitors in BCG-unresponsive nonmuscle invasive bladder cancer: can they help spare the bladder?

Intravesical BCG therapy has been for years, the standard of care in nonmuscle-invasive bladder cancer. But upon recurrence/relapse, radical cystectomy is imposed, due to the paucity of other therapeutic options. Immunotherapy has been revolutionizing cancer treatment, and its indications continue to broaden. It has been approved for the treatment of advanced urothelial cancer of the bladder, mainly as a second-line therapy. Its activity is being studied in nonmuscle-invasive bladder cancer that is not responsive to BCG; we herein report the trials investigating these checkpoint inhibitors (pembrolizumab, nivolumab, atezolizumab, durvalumab and avelumab) in this particular setting.

Reliable chromatographic assay for measuring of indoleamine 2,3-dioxygenase 1 (IDO1) activity in human cancer cells

The kynurenine pathway is the major tryptophan degradation routes generating bioactive compounds important in physiology and diseases. Depending on cell type it is initiated enzymatically by tryptophan-2,3-dioxygenase (TDO) or indoleamine-2,3-dioxygenase 1 and 2 (IDO1 and IDO2) to yield N-formylkynurenine as the precursor of further metabolites. Herein, we describe an accurate high-pressure liquid chromatography coupled with a diode array detector (HPLC-DAD) method to serve for IDO1 activity determination in human cancer cells cultured in vitro. Enzymatic activity was expressed as the rate of ʟ-kynurenine generation by 1 mg of proteins obtained from cancer cells. Our approach shows the limit of detection and limit of quantification at 12.9 and 43.0 nM Kyn, respectively. Applicability of this method was demonstrated in different cells (ovarian and breast cancer)exposed to various conditions and has successfully passed the validation process. This approach presents a useful model to study the role of kynurenine pathway in cancer biology.

Blockade of IDO-Kynurenine-AhR Axis Ameliorated Colitis-Associated Colon Cancer via Inhibiting Immune Tolerance

BACKGROUND & AIMS

Chronic inflammation in colon section is associated with an increased risk of colorectal cancer (CRC). Proinflammatory cytokines were produced in a tumor microenvironment and correlated with poor clinical outcome. Tumor-infiltrating T cells were reported to be greatly involved in the development of colon cancer. In this study, we demonstrated that kynurenine (Kyn), a metabolite catalyzed by indoleamine 2,3-dioxygenase (IDO), was required for IDO-mediated T cell function, and adaptive immunity indeed played a critical role in CRC.

METHODS

Supernatant of colon cancer cells was used to culture activated T cells and mice spleen lymphocytes, and the IDO1-Kyn-aryl hydrocarbon (AhR) receptor axis was determined in vitro. In vivo, an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CRC model was established in IDO-/-, Rag1-/-, and wild-type mice, and tumor-associated T lymphocyte infiltration and Kyn/AhR signaling pathway changes were measured in each group.

RESULTS

Kyn promoted AhR nuclear translocation increased the transcription of Foxp3, a marker of regulatory T cells (Tregs), through improving the interaction between AhR and Foxp3 promoter. Additionally, compared WT mice, IDO-/- mice treated with AOM/DSS exhibited fewer and smaller tumor burdens in the colon, with less Treg and more CD8+ T cells infiltration, while Kyn administration abolished this regulation. Rag1-/- mice were more sensitive to AOM/DSS-induced colitis-associated colon cancer (CRC) compared with the wild-type mice, suggesting that T cell-mediated adaptive immunity indeed played a critical role in CRC.

CONCLUSIONS

We demonstrated that inhibition of IDO diminished Kyn/AhR-mediated Treg differentiation and could be an effective strategy for the prevention and treatment of inflammation-related colon cancer.

New Insights into Endometrial Cancer

EC is the most common cancer in the female genital tract in developed countries, and with its increasing incidence due to risk factors, such as aging and obesity, tends to become a public health issue. Although EC is a hormone-dependent neoplasm, there are no recommendations for the determination of steroid hormone receptors in the tumor tissue and no hormone therapy has ever been assessed in the adjuvant setting. Furthermore, its immune environment has been slightly characterized, but recent evidences point out how EC microenvironment may increase self-tolerance by reducing the recruitment of cytotoxic immune cells to the tumor site and/or modifying their phenotype, making these cells no longer able to suppress tumor growth. Here we highlight insights for EC management from diagnosis to a desirable trend of personalized treatment.

Aryl hydrocarbon receptor: Its roles in physiology

Aryl hydrocarbon receptor (AHR) was initially discovered as a cellular protein involved in mediating the detoxification of xenobiotic compounds. Extensive research in the past two decades has identified several families of physiological ligands and uncovered important functions of AHR in normal development and homeostasis. Deficiency in AHR expression disrupts major signaling systems and transcriptional programs, which appear to be responsible for the development of numerous developmental abnormalities including cardiac hypertrophy and epidermal hyperplasia. This mini review primarily summarizes recent advances in our understanding of AHR functions in normal physiology with an emphasis on the cardiovascular, gastrointestinal, integumentary, nervous, and immunomodulatory systems.

Dendritic Cells of Leukemic Origin: Specialized Antigen-Presenting Cells as Potential Treatment Tools for Patients with Myeloid Leukemia

The prognosis of elderly patients with acute myeloid leukemia (AML) and high-grade myelodysplastic syndrome (MDS) is limited due to the lack of therapy options and high relapse rates. Dendritic cell (DC)-based immunotherapy seems to be a promising treatment tool. DC are potent antigen-presenting cells and play a pivotal role on the interface of the innate and the adaptive immune system. Myeloid leukemia blasts can be converted to DC of leukemic origin (DC_leu), expressing costimulatory molecules along with the whole leukemic antigen repertoire of individual patients. These generated DC_leu are potent stimulators of various immune reactive cells and increase antileukemic immunity ex vivo. Here we review the generating process of DC/DC_leu from leukemic peripheral blood mononuclear cells as well as directly from leukemic whole blood with "minimized" Kits to simulate physiological conditions ex vivo. The purpose of adoptive cell transfer of DC/DC_leu as a vaccination strategy is discussed. A new potential therapy option with Kits for patients with myeloid leukemia, which would render an adoptive DC/DC_leu transfer unnecessary, is presented. In summary, DC/DC_leu-based therapies seem to be promising treatment tools for patients with AML or MDS but ongoing research including trials in animals and humans have to be performed.

Saturated Fatty Acid Intake Is Associated With Increased Inflammation, Conversion of Kynurenine to Tryptophan, and Delta-9 Desaturase Activity in Healthy Humans

Saturated fat ingestion has previously been linked to increases in inflammation. However the relationship between saturated fatty acid (SFA) intake and the kynureine:tryptophan ratio ([Kyn]:[Trp]), a marker of inflammation, has not been previously investigated. This study evaluated in healthy, middle aged, individuals (men = 48, women = 52), potential relationships between SFA intake, red blood cell (RBC) membrane SFAs and monounsaturated fatty acids (MUFA), the [Kyn]:[Trp] ratio, C-reactive protein (CRP), TNF-α and Δ9 desaturase activity. [Kyn]:[Trp] was positively associated with increases in Total fat (P = .034) intake, including Total SFA (P = .029) and Total MUFA (P = .042) intakes. Unexpectedly the [Kyn]:[Trp] ratio was inversely associated with the percentage of Total SFA (P = .004) and positively associated with percentage of Total MUFA (P = .012) present in the RBC membrane. We found a positive association between Δ9 desaturase activity, responsible for the desaturation of a various SFAs to MUFAs, and [Kyn]:[Trp] (P = .008). [Kyn]:[Trp] was also positively associated with CRP (P = .044), however no significant relationship between [Kyn]:[Trp] and TNF-α was found. This study shows for the first time that SFA consumption increases inflammatory pathways linked to increased tryptophan to kynurenine conversion, even in healthy humans. Our data also suggests that SFA linked increases in inflammation occur concomitantly with an upregulation of Δ9 desaturase activity resulting in increased desaturation of SFA substrates to their MUFA derivatives.

Depression, Estrogens, and Neuroinflammation: A Preclinical Review of Ketamine Treatment for Mood Disorders in Women

Ketamine has been shown to acutely and rapidly ameliorate depression symptoms and suicidality. Given that women suffer from major depression at twice the rate of men, it is important to understand how ketamine works in the female brain. This review explores three themes. First, it examines our current understanding of the etiology of depression in women. Second, it examines preclinical research on ketamine's antidepressant effects at a neurobiological level as well as how ovarian hormones present a unique challenge in interpreting these findings. Lastly, the neuroinflammatory hypothesis of depression is highlighted to help better understand how ovarian hormones might interact with ketamine in the female brain.

Indoleamine 2,3-Dioxygenase Activity-Induced Acceleration of Tumor Growth, and Protein Kinases-Related Novel Therapeutics Regimens

Indoleamine 2,3-dioxygenase (IDO) is overexpressed in response to interferon-gamma (IFN-γ). IDO-mediated degradation of tryptophan (Trp) along the kynurenine (Kyn) pathway by immune cells is associated with the anti-microbial, and anti-tumor defense mechanisms. In contrast, IDO is constitutively expressed by various tumors and creates an immunosuppressive microenvironment around the tumor tissue both by depletion of the essential amino acid Trp and by formation of Kyn, which is immunosuppressive metabolite of Trp. IDO may activate its own expression in human cancer cells via an autocrine aryl hydrocarbon receptor (AhR)- interleukin 6 (IL-6)-signal transducer and activator of transcription 3 (STAT3) signaling loop. Although IDO is not a unique marker, in many clinical trials serum IDO activity is suggested to be an important parameter in the pathogenesis of cancer development and growth. Measuring IDO activity in serum seems to be an indicator of cancer growth rate, however, it is controversial whether this approach can be used as a reliable guide in cancer patients treated with IDO inhibitors. Thus, IDO immunostaining is strongly recommended for the identification of higher IDO producing tumors, and IDO inhibitors should be included in post-operative complementary therapy in IDO positive cancer cases only. Novel therapies that target the IDO pathway cover checkpoint protein kinases related combination regimens. Currently, multi-modal therapies combining IDO inhibitors and checkpoint kinase blockers in addition to T regulatory (Treg) cell-modifying treatments seem promising.

A Review of Immune Checkpoint Blockade Therapy in Endometrial Cancer

Approximately 30% of primary endometrial cancers are microsatellite instability high/hypermutated (MSI-H), and 13% to 30% of recurrent endometrial cancers are MSI-H or mismatch repair deficient (dMMR). Given the presence of immune dysregulation in endometrial cancer as described, immune checkpoint blockade (ICB) has been explored as a therapeutic mechanism, both as monotherapy and in combination with cytotoxic chemotherapy, other immunotherapy, or targeted agents. In MSI-H or dMMR advanced endometrial cancers, PD-1 inhibitors dostarlimab and pembrolizumab have shown response rates of 49% and 57%, respectively, whereas PD-L1 inhibitors avelumab and durvalumab have shown response rates of 27% and 43%, respectively. In microsatellite stable (MSS) or PD-L1-positive advanced endometrial cancers, modest activity of PD-1 inhibitors nivolumab and dostarlimab and PD-L1 inhibitors atezolizumab, avelumab, and durvalumab has been seen, with response rates ranging from 3% to 23%. Based on substantial activity in a phase Ib/II study, the U.S. Food and Drug Administration (FDA) granted lenvatinib and pembrolizumab combination therapy accelerated approval in 2019 for the treatment of advanced endometrial cancer that is not MSI-H or dMMR and has progressed following prior therapy. Although these developments have been highly impactful, a more robust understanding of the molecular and immunologic drivers of response and resistance will be critical to optimally design next-generation studies in endometrial cancer.

Pembrolizumab for the treatment of uveal melanoma: A case series

Uveal melanoma is a rare disease. Up to 50% of the patients will develop metastases for which the treatment options are limited. No randomized controlled data for the treatment of uveal melanoma patients are available. In this study we describe the clinical course of nine uveal melanoma patients included in the pembrolizumab expanded access program (EAP) in Belgium. Nine uveal melanoma patients were treated in the EAP with 2mg/kg pembrolizumab every 3 weeks. Patients received pembrolizumab as first or second-line treatment. Baseline characteristics and tumor responses were prospectively collected. During a median follow-up of 40 weeks, the estimated median PFS was 18 weeks (95% CI 0.7–35) and median OS was 46 weeks (95% CI 33–59%). Four patients had stable disease (SD) for more than 20 weeks (PFS of 21, 22, and 27 weeks respectively) and 1 patient presented with SD for 119 weeks. No objective responses according to irRC were observed. One grade 3 hepatitis occurred which was reversible with the administration of high doses oral corticosteroids. Even though treatment with pembrolizumab is well tolerated, clinical benefit is disappointing. Nevertheless long-term diseases control can be achieved in selected cases

A comprehensive review on β-lapachone: Mechanisms, structural modifications, and therapeutic potentials

β-Lapachone (β-lap, 1), an ortho-naphthoquinone natural product isolated from the lapacho tree (Tabebuia avellanedae) in many regions of South America, has received extensive attention due to various pharmacological activities, such as antitumor, anti-Trypanosoma cruzi, anti-Mycobacterium tuberculosis, antibacterial, and antimalarial activities. Related mechanisms of β-lap have been widely investigated for a full understanding of its therapeutic potentials. Numerous derivatives of β-lap have been reported with aims to generate new chemical entities, improve the corresponding biological potency, and overcome disadvantages of its physical and chemical properties and safety profiles. This review will give insight into the pharmacological mechanisms of β-lap and provide a comprehensive understanding of its structural modifications with regard to different therapeutic potentials. The available clinical trials related to β-lap and its derivatives are also summarized.

Analysis of Postdeployment Serum Samples Identifies Potential Biomarkers of Exposure to Burn Pits and Other Environmental Hazards

OBJECTIVE

The potential health risks of deployment to sites with open burn pits remain poorly understood, in part, because personal exposure monitoring was not performed. Here, we investigated whether postdeployment serum samples contain biomarkers associated with exposure to burn pits.

METHODS

A total of 237 biomarkers were measured in 800 serum samples from deployed and never-deployed subjects. We used a regression model and a supervised vector machine to identify serum biomarkers with significant associations with exposures and deployment.

RESULTS

We identified 101 serum biomarkers associated with polycyclic aromatic hydrocarbons, dioxins or furans, and 54 biomarkers associated with deployment. Twenty-six of these biomarkers were shared in common by the exposure and deployment groups.

CONCLUSIONS

We identify a potential signature of exposure to open burn pits, and provide a framework for using postexposure sera to identify exposures when contemporaneous monitoring was inadequate.

Current Status of Clinical Trials for Cervical and Uterine Cancer Using Immunotherapy Combined With Radiation

Novel therapies combined with radiation continue to be of significant interest in the developmental treatment paradigm of gynecologic cancers. Clinical implementation of immunotherapy in oncology has rapidly changed the treatment landscape, options, paradigm, and outcomes through clinical trials. Immunotherapy has emerged as a therapeutic pillar in the treatment of solid tumors with demonstrable synergistic activity when combined with radiation therapy and chemoradiotherapy by an alteration or enhancement of the immune system. In solid tumors, radiation therapy induces migration of dendritic cells, T cell activation, and proliferation, and increases in tumor-infiltrating lymphocytes. These immunomodulatory effects in conjunction with immune checkpoint blockade are currently under active investigation in the adjuvant, definitive, and metastatic settings. Results from early phase trials demonstrate promising efficacy and overall tolerable toxicity profiles of combined modality treatment. There is significant interest in optimizing the treatment for patients with locally advanced cervical cancer beyond the standard of care-chemoradiation-which has been in place for the last 30 years. The majority of cervical cancer emerges after persistent infection with a high-risk subtype of the human papillomavirus, where viral oncoproteins lead to cellular changes and immortalization. As a result, immune tolerance can develop, resulting in cancer. Knowledge of the mechanism of human papillomavirus-related oncogenesis suggests that immune therapy or checkpoint blockade can reinvigorate an antitumor immune response. Current clinical trials are exploring the therapeutic potential of these approaches. Uterine cancers have been grouped into 4 molecular subclasses by their driver mutations, mutational burden, and copy-number alterations. Of these subgroups, the polymerase epsilon-mutated and microsatellite-unstable may represent up to 40% of endometrial cancers, and they have been shown to be immunogenic. Because of the inherent immunogenicity of these MSI-high tumors, combined immune modulation strategies, including chemotherapy, radiation, and immunotherapy and immune checkpoint inhibitor therapy, are being explored to improve treatment outcomes. In this review, we explore current immunomodulatory and multimodality therapeutic approaches in the treatment of cervical and uterine cancer through ongoing clinical trials investigating the combination of immunotherapy and radiation therapy.

Redox control in the pathophysiology of influenza virus infection

Triggered in response to external and internal ligands in cells and animals, redox homeostasis is transmitted via signal molecules involved in defense redox mechanisms through networks of cell proliferation, differentiation, intracellular detoxification, bacterial infection, and immune reactions. Cellular oxidation is not necessarily harmful per se, but its effects depend on the balance between the peroxidation and antioxidation cascades, which can vary according to the stimulus and serve to maintain oxygen homeostasis. The reactive oxygen species (ROS) that are generated during influenza virus (IV) infection have critical effects on both the virus and host cells. In this review, we outline the link between viral infection and redox control using IV infection as an example. We discuss the current state of knowledge on the molecular relationship between cellular oxidation mediated by ROS accumulation and the diversity of IV infection. We also summarize the potential anti-IV agents available currently that act by targeting redox biology/pathophysiology.

Recombinant Lactaptin Induces Immunogenic Cell Death and Creates an Antitumor Vaccination Effect in Vivo with Enhancement by an IDO Inhibitor

Natural compounds of various origins are intensively investigated for their antitumor activity. Potential benefits of antitumor therapy can be achieved when cytotoxic agents kill cancer cells and these dying cancer cells drive adoptive immunity to the tumor. This strategy was successfully demonstrated for chemotherapeutic drugs that induce immunogenic type of cell death (ICD) with release of DAMPs (danger associated molecular patterns) and exposure of “eat me” signals. In this study, we demonstrated that recombinant human milk peptide lactaptin (RL2) induces death of cancer cells with ICD hallmarks in vitro with the release of ATP and high-mobility group box 1 protein (HMGB1) and exposure of calreticulin and HSP70 on the external cell membrane. RL2-treated cancer cells were efficiently engulfed by phagocytic cells. Using the syngeneic mouse model, we demonstrated that RL2-treated MX-7 rhabdomyosarcoma cells confer long-term immune-mediated protection against challenge with live MX-7 cells. We also analyzed the combinatorial antitumor effect of vaccination with RL2-treated cells and the inhibition of indoleamine 2,3-dioxygenase (IDO) with ethyl pyruvate. Compared to solo anti-tumor immunization with RL2-treated cells, additional chemical inhibition of IDO demonstrated better long-term antitumor responses than vaccination alone.

Improving long-term survival in diffuse intrinsic pontine glioma

INTRODUCTION

Diffuse intrinsic pontine glioma (DIPG) is an almost universally fatal pediatric brain cancer. There has been no improvement in event-free survival (EFS) or overall survival (OS) despite immense effort through a multitude of clinical trials to find a cure. Recently, there has been a surge in the knowledge of DIPG biology, including the discovery of a recurrent H3F3A mutation in over 80% of these tumors.

AREAS COVERED

The authors review the most recent approaches to diagnosis and treatment of DIPG including chemotherapy, biologics, surgical approaches, and immunotherapy.

EXPERT OPINION

The authors propose four main opportunities to improve long-term survival. First, patients should be enrolled in scientifically sound clinical trials that include molecularly profiling either via stereotactic biopsy or liquid biopsy. Second, clinical trials should include more innovative endpoints other than traditional EFS and OS such as MRI/PET imaging findings combined with surrogates of activity (e.g. serial liquid biopsies) to better ascertain biologically active treatments. Third, innovative clinical trial approaches are needed to help allow for the rapid development of combination therapies to be tested. Finally, effort should be concentrated on reversing the effects of the histone mutation, as this malfunctioning development program seems to be key to DIPG relentlessness.

Increased effect of two-fraction radiotherapy in conjunction with IDO1 inhibition in experimental glioblastoma

Objectives

The 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.

Methods

Gene 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.

Results

The 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.

Conclusions

Addition 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 knowledge

The 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.

Dual-Blockade Immune Checkpoint for Breast Cancer Treatment Based on a Tumor-Penetrating Peptide Assembling Nanoparticle

Cancer immunotherapy can enhance the antitumor effect of drugs through a combinatorial approach in a synergistic manner. However, the effective targeted delivery of various drugs remains a challenge. We generated a peptide assembling tumor-targeted nanodelivery system based on a breast cancer homing and penetrating peptide for the codelivery of a programmed cell death ligand 1 (PD-L1) small interfering RNA (siRNA) (siPD-L1) and an indoleamine 2,3-dioxygenase inhibitor as a dual blockade of an immune checkpoint. The vector is capable of specifically accumulating in the breast cancer tumor site in a way that allows the siRNA to escape from endosomal vesicles after being endocytosed by tumor cells. The drug within these cells then acts to block tryptophan metabolism. The results showed that locally released siPD-L1 and 1-methyl-dl-tryptophan favor the survival and activation of cytotoxic T lymphocytes, resulting in apoptosis of breast cancer cells. Therefore, this study provides a potential approach for treating breast cancer by blocking immunological checkpoints through the assembly of micelles with functional peptides.

T Regulatory Cells and Priming the Suppressive Tumor Microenvironment

Treg play a central role in maintenance of self tolerance and homeostasis through suppression of self-reactive T cell populations. In addition to that role, Treg also survey cancers and suppress anti-tumor immune responses. Thus, understanding the unique attributes of Treg-tumor interactions may permit control of this pathologic suppression without interfering with homeostatic self-tolerance. This review will define the unique role of Treg in cancer growth, and the ways by which Treg inhibit a robust anti-tumor immune response. There will be specific focus placed on Treg homing to the tumor microenvironment (TME), TME formation of induced Treg (iTreg), mechanisms of suppression that underpin cancer immune escape, and trophic nonimmunologic effects of Treg on tumor cells.

Effects of the Novel IDO Inhibitor DWG-1036 on the Behavior of Male and Female 3xTg-AD Mice

The kynurenine pathway metabolizes tryptophan into nicotinamide adenine dinucleotide, producing a number of intermediary metabolites, including 3-hydroxy kynurenine and quinolinic acid, which are involved in the neurodegenerative mechanisms that underlie Alzheimer's disease (AD). Indolamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of this pathway, is increased in AD, and it has been hypothesized that blocking this enzyme may slow the progression of AD. In this study, we treated male and female 3xTg-AD and wild-type mice with the novel IDO inhibitor DWG-1036 (80 mg/kg) or vehicle (distilled water) from 2 to 6 months of age and then tested them in a battery of behavioral tests that measured spatial learning and memory (Barnes maze), working memory (trace fear conditioning), motor coordination and learning (rotarod), anxiety (elevated plus maze), and depression (tail suspension test). The 3xTg-AD mice treated with DWG-1036 showed better memory in the trace fear conditioning task and significant improvements in learning but poorer spatial memory in the Barnes maze. DWG-1036 treatment also ameliorated the behaviors associated with increased anxiety in the elevated plus maze and depression-like behaviors in the tail suspension test in 3xTg-AD mice. However, the effects of DWG-1036 treatment on the behavioral tasks were variable, and sex differences were apparent. In addition, high doses of DWG-1036 resulted in reduced body weight, particularly in females. Taken together, our results suggest that the kynurenine pathway is a promising target for treating AD, but more work is needed to determine the effective compounds, examine sex differences, and understand the side effects of the compounds.

Integrated Pan-Cancer Map of EBV-Associated Neoplasms Reveals Functional Host-Virus Interactions

Epstein-Barr virus (EBV) is a complex oncogenic symbiont. The molecular mechanisms governing EBV carcinogenesis remain elusive and the functional interactions between virus and host cells are incompletely defined. Here we present a comprehensive map of the host cell-pathogen interactome in EBV-associated cancers. We systematically analyzed RNA sequencing from >1,000 patients with 15 different cancer types, comparing virus and host factors of EBV⁺ to EBV^- tissues. EBV preferentially integrated at highly accessible regions of the cancer genome, with significant enrichment in super-enhancer architecture. Twelve EBV transcripts, including LMP1 and LMP2, correlated inversely with EBV reactivation signature. Overexpression of these genes significantly suppressed viral reactivation, consistent with a "virostatic" function. In cancer samples, hundreds of novel frequent missense and nonsense variations in virostatic genes were identified, and variant genes failed to regulate their viral and cellular targets in cancer. For example, one-third of patients with EBV⁺ NK/T-cell lymphoma carried two novel nonsense variants (Q322X, G342X) of LMP1 and both variant proteins failed to restrict viral reactivation, confirming loss of virostatic function. Host cell transcriptional changes in response to EBV infection classified tumors into two molecular subtypes based on patterns of IFN signature genes and immune checkpoint markers, such as PD-L1 and IDO1. Overall, these findings uncover novel points of interaction between a common oncovirus and the human genome and identify novel regulatory nodes and druggable targets for individualized EBV and cancer-specific therapies. SIGNIFICANCE: This study provides a comprehensive map of the host cell-pathogen interactome in EBV⁺ malignancies.See related commentary by Mbulaiteye and Prokunina-Olsson, p. 5917.