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Choi J, Park B, Park JY, Shin D, Lee S, Yoon HY, Kim K, Kim SH, Kim Y, Yang Y, Shim MK. Light-Triggered PROTAC Nanoassemblies for Photodynamic IDO Proteolysis in Cancer Immunotherapy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2405475. [PMID: 38898702 DOI: 10.1002/adma.202405475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Revised: 05/30/2024] [Indexed: 06/21/2024]
Abstract
While proteolysis-targeting chimeras (PROTACs) hold great potential for persistently reprogramming the immunosuppressive tumor microenvironment via targeted protein degradation, precisely activating them in tumor tissues and preventing uncontrolled proteolysis at off-target sites remain challenging. Herein, a light-triggered PROTAC nanoassembly (LPN) for photodynamic indoleamine 2,3-dioxygenase (IDO) proteolysis is reported. The LPN is derived from the self-assembly of prodrug conjugates, which comprise a PROTAC, cathepsin B-specific cleavable peptide linker, and photosensitizer, without any additional carrier materials. In colon tumor models, intravenously injected LPNs initially silence the activity of PROTACs and accumulate significantly in targeted tumor tissues due to an enhanced permeability and retention effect. Subsequently, the cancer biomarker cathepsin B begins to trigger the release of active PROTACs from the LPNs through enzymatic cleavage of the linkers. Upon light irradiation, tumor cells undergo immunogenic cell death induced by photodynamic therapy to promote the activation of effector T cells, while the continuous IDO degradation of PROTAC simultaneously blocks tryptophan metabolite-regulated regulatory-T-cell-mediated immunosuppression. Such LPN-mediated combinatorial photodynamic IDO proteolysis effectively inhibits tumor growth, metastasis, and recurrence. Collectively, this study presents a promising nanomedicine, designed to synergize PROTACs with other immunotherapeutic modalities, for more effective and safer cancer immunotherapy.
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Affiliation(s)
- Jiwoong Choi
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
| | - Byeongmin Park
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
| | - Jung Yeon Park
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
| | - Dongwon Shin
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
| | - Sangmin Lee
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Kyung Hee University, Seoul, 02453, Republic of Korea
| | - Hong Yeol Yoon
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
| | - Kwangmeyung Kim
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul, 03760, Republic of Korea
| | - Sun Hwa Kim
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
| | - Yongju Kim
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
- Chemical and Biological Integrative Research Center, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
| | - Yoosoo Yang
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
- Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology, Seoul, 02792, Republic of Korea
| | - Man Kyu Shim
- Medicinal Materials Research Center, Biomedical Research Division, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
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Yu L, Xu L, Chen Y, Rong Y, Zou Y, Ge S, Wu T, Lai Y, Xu Q, Guo W, Liu W. IDO1 Inhibition Promotes Activation of Tumor-intrinsic STAT3 Pathway and Induces Adverse Tumor-protective Effects. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2024; 212:1232-1243. [PMID: 38391297 DOI: 10.4049/jimmunol.2300545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 01/02/2024] [Indexed: 02/24/2024]
Abstract
Pharmacological inhibition of IDO1 exhibits great promise as a strategy in cancer therapy. However, the failure of phase III clinical trials has raised the pressing need to understand the underlying reasons for this outcome. To gain comprehensive insights into the reasons behind the clinical failure of IDO1 inhibitors, it is essential to investigate the entire tumor microenvironment rather than focusing solely on individual cells or relying on knockout techniques. In this study, we conducted single-cell RNA sequencing to determine the overall response to apo-IDO1 inhibitor administration. Interestingly, although apo-IDO1 inhibitors were found to significantly activate intratumoral immune cells (mouse colon cancer cell CT26 transplanted in BALB/C mice), such as T cells, macrophages, and NK cells, they also stimulated the infiltration of M2 macrophages. Moreover, these inhibitors prompted monocytes and macrophages to secrete elevated levels of IL-6, which in turn activated the JAK2/STAT3 signaling pathway in tumor cells. Consequently, this activation enables tumor cells to survive even in the face of heightened immune activity. These findings underscore the unforeseen adverse effects of apo-IDO1 inhibitors on tumor cells and highlight the potential of combining IL-6/JAK2/STAT3 inhibitors with apo-IDO1 inhibitors to improve their clinical efficacy.
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Affiliation(s)
- Longbo Yu
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
| | - Lingyan Xu
- Department of Oncology and Cancer Rehabilitation Centre, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yunjie Chen
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
| | - Yicheng Rong
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
| | - Yi Zou
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Drug Discovery, China Pharmaceutical University, Nanjing, China
| | - Shushan Ge
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Drug Discovery, China Pharmaceutical University, Nanjing, China
| | - Tiancong Wu
- Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Yisheng Lai
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Drug Discovery, China Pharmaceutical University, Nanjing, China
| | - Qiang Xu
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
| | - Wenjie Guo
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
| | - Wen Liu
- State Key Laboratory of Pharmaceutical Biotechnology, Chemistry and Biomedicine Innovation Center, School of Life Sciences, Nanjing University, Nanjing, China
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Orecchini E, Belladonna ML, Pallotta MT, Volpi C, Zizi L, Panfili E, Gargaro M, Fallarino F, Rossini S, Suvieri C, Macchiarulo A, Bicciato S, Mondanelli G, Orabona C. The signaling function of IDO1 incites the malignant progression of mouse B16 melanoma. Oncoimmunology 2023; 12:2170095. [PMID: 36733497 PMCID: PMC9888476 DOI: 10.1080/2162402x.2023.2170095] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Indoleamine 2,3 dioxygenase 1 (IDO1), a leader tryptophan-degrading enzyme, represents a recognized immune checkpoint molecule. In neoplasia, IDO1 is often highly expressed in dendritic cells infiltrating the tumor and/or in tumor cells themselves, particularly in human melanoma. In dendritic cells, IDO1 does not merely metabolize tryptophan into kynurenine but, after phosphorylation of critical tyrosine residues in the non-catalytic small domain, it triggers a signaling pathway prolonging its immunoregulatory effects by a feed-forward mechanism. We here investigated whether the non-enzymatic function of IDO1 could also play a role in tumor cells by using B16-F10 mouse melanoma cells transfected with either the wild-type Ido1 gene (Ido1WT ) or a mutated variant lacking the catalytic, but not signaling activity (Ido1H350A ). As compared to the Ido1WT -transfected counterpart (B16WT), B16-F10 cells expressing Ido1H350A (B16H350A) were characterized by an in vitro accelerated growth mediated by increased Ras and Erk activities. Faster growth and malignant progression of B16H350A cells, also detectable in vivo, were found to be accompanied by a reduction in tumor-infiltrating CD8+ T cells and an increase in Foxp3+ regulatory T cells. Our data, therefore, suggest that the IDO1 signaling function can also occur in tumor cells and that alternative therapeutic approach strategies should be undertaken to effectively tackle this important immune checkpoint molecule.
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Affiliation(s)
- E Orecchini
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - ML Belladonna
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - MT Pallotta
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - C Volpi
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - L Zizi
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - E Panfili
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - M Gargaro
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - F Fallarino
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - S Rossini
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - C Suvieri
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - A Macchiarulo
- Department of Pharmaceutical Sciences, University of Perugia, Perugia, Italy
| | - S Bicciato
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - G Mondanelli
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - C Orabona
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy,CONTACT C Orabona Department of Medicine and Surgery, University of Perugia, Piazza Severi, Perugia06129, Italy
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Akter Z, Salamat N, Ali MY, Zhang L. The promise of targeting heme and mitochondrial respiration in normalizing tumor microenvironment and potentiating immunotherapy. Front Oncol 2023; 12:1072739. [PMID: 36686754 PMCID: PMC9851275 DOI: 10.3389/fonc.2022.1072739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 12/12/2022] [Indexed: 01/07/2023] Open
Abstract
Cancer immunotherapy shows durable treatment responses and therapeutic benefits compared to other cancer treatment modalities, but many cancer patients display primary and acquired resistance to immunotherapeutics. Immunosuppressive tumor microenvironment (TME) is a major barrier to cancer immunotherapy. Notably, cancer cells depend on high mitochondrial bioenergetics accompanied with the supply of heme for their growth, proliferation, progression, and metastasis. This excessive mitochondrial respiration increases tumor cells oxygen consumption, which triggers hypoxia and irregular blood vessels formation in various regions of TME, resulting in an immunosuppressive TME, evasion of anti-tumor immunity, and resistance to immunotherapeutic agents. In this review, we discuss the role of heme, heme catabolism, and mitochondrial respiration on mediating immunosuppressive TME by promoting hypoxia, angiogenesis, and leaky tumor vasculature. Moreover, we discuss the therapeutic prospects of targeting heme and mitochondrial respiration in alleviating tumor hypoxia, normalizing tumor vasculature, and TME to restore anti-tumor immunity and resensitize cancer cells to immunotherapy.
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Wang PF, Yang LQ, Shi ZH, Li XM, Qiu HY. An updated patent review of IDO1 inhibitors for cancer (2018-2022). Expert Opin Ther Pat 2022; 32:1145-1159. [PMID: 36420761 DOI: 10.1080/13543776.2022.2151894] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Indoleamine 2,3-dioxygenase 1 (IDO1) is highly related to the immune evasion of a wide range of malignancies due to its role in the immune suppression caused by the depletion of tryptophan (Trp) and the accumulation of kynurenine (Kyn). The combination of IDO1 inhibitors with other treatments represents a promising strategy in immunotherapy, although considerable challenges lie ahead. AREAS COVERED This review focuses on patent publications searched from Espacenet and Google Scholar, and related to IDO1 inhibitors with potential anti-cancer utilization during the period 2018-2022. EXPERT OPINION Despite the clinical trial failure of the first-in-class IDO1 inhibitor epacadostat in combination with pembrolizumab, numerous studies have been carried on to pursue more efficient IDO1-based immune-modulating therapeutic solutions. A large number of IDO1 inhibitors with new structures and design concepts have been produced with the impetus of crystallographic studies, and have shown great research potential. The elaboration on the combination of IDO1 inhibitors with other targeting agents, the more precise selection of patients, the identification of more reliable biomarkers for evaluating the IDO1 treatment, and the investigation of possible toxicity, are critical factors to promote IDO1-based immunotherapies from bench to bedside.
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Affiliation(s)
- Peng-Fei Wang
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, People's Republic of China
| | - Li-Qiang Yang
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, People's Republic of China
| | - Zhao-Hang Shi
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, People's Republic of China
| | - Xue-Min Li
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, People's Republic of China
| | - Han-Yue Qiu
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, People's Republic of China
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Pallotta MT, Rossini S, Suvieri C, Coletti A, Orabona C, Macchiarulo A, Volpi C, Grohmann U. Indoleamine 2,3-dioxygenase 1 (IDO1): an up-to-date overview of an eclectic immunoregulatory enzyme. FEBS J 2022; 289:6099-6118. [PMID: 34145969 PMCID: PMC9786828 DOI: 10.1111/febs.16086] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/04/2021] [Accepted: 06/18/2021] [Indexed: 12/30/2022]
Abstract
Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the initial rate-limiting step in the degradation of the essential amino acid tryptophan along the kynurenine pathway. When discovered more than 50 years ago, IDO1 was thought to be an effector molecule capable of mediating a survival strategy based on the deprivation of bacteria and tumor cells of the essential amino acid tryptophan. Since 1998, when tryptophan catabolism was discovered to be crucially involved in the maintenance of maternal T-cell tolerance, IDO1 has become the focus of several laboratories around the world. Indeed, IDO1 is now considered as an authentic immune regulator not only in pregnancy, but also in autoimmune diseases, chronic inflammation, and tumor immunity. However, in the last years, a bulk of new information-including structural, biological, and functional evidence-on IDO1 has come to light. For instance, we now know that IDO1 has a peculiar conformational plasticity and, in addition to a complex and highly regulated catalytic activity, is capable of performing a nonenzymic function that reprograms the expression profile of immune cells toward a highly immunoregulatory phenotype. With this state-of-the-art review, we aimed at gathering the most recent information obtained for this eclectic protein as well as at highlighting the major unresolved questions.
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Affiliation(s)
| | - Sofia Rossini
- Department of Medicine and SurgeryUniversity of PerugiaItaly
| | - Chiara Suvieri
- Department of Medicine and SurgeryUniversity of PerugiaItaly
| | - Alice Coletti
- Department of Pharmaceutical SciencesUniversity of PerugiaItaly
| | - Ciriana Orabona
- Department of Medicine and SurgeryUniversity of PerugiaItaly
| | | | - Claudia Volpi
- Department of Medicine and SurgeryUniversity of PerugiaItaly
| | - Ursula Grohmann
- Department of Medicine and SurgeryUniversity of PerugiaItaly
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7
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Biswas P, Dai Y, Stuehr DJ. Indoleamine dioxygenase and tryptophan dioxygenase activities are regulated through GAPDH- and Hsp90-dependent control of their heme levels. Free Radic Biol Med 2022; 180:179-190. [PMID: 35051612 DOI: 10.1016/j.freeradbiomed.2022.01.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/08/2021] [Accepted: 01/11/2022] [Indexed: 01/15/2023]
Abstract
Indoleamine-2, 3-dioxygenase (IDO1) and Tryptophan-2, 3-dioxygense (TDO) are heme-containing dioxygenases that catalyze the conversion of tryptophan to N-formyl-kynurenine and thus enable generation of l-kynurenine and related metabolites that govern the immune response and broadly impact human biology. Given that TDO and IDO1 activities are directly proportional to their heme contents, it is important to understand their heme delivery and insertion processes. Early studies established that TDO and IDO1 heme levels are sub-saturating in vivo and subject to change but did not identify the cellular mechanisms that provide their heme or enable dynamic changes in their heme contents. We investigated the potential involvement of GAPDH and chaperone Hsp90, based on our previous studies linking these proteins to intracellular heme allocation. We studied heme delivery and insertion into IDO1 and TDO expressed in both normal and heme-deficient HEK293T cells and into IDO1 naturally expressed in HeLa cells in response to IFN-γ, and also investigated the interactions of TDO and IDO1 with GAPDH and Hsp90 in cells and among their purified forms. We found that GAPDH delivered both mitochondrially-generated and exogenous heme to apo-IDO1 and apo-TDO in cells, potentially through a direct interaction with either enzyme. In contrast, we found Hsp90 interacted with apo-IDO1 but not with apo-TDO, and was only needed to drive heme insertion into apo-IDO1. By uncovering the cellular processes that allocate heme to IDO1 and TDO, our study provides new insight on how their activities and l-kynurenine production may be controlled in health and disease.
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Affiliation(s)
- Pranjal Biswas
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, USA
| | - Yue Dai
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, USA
| | - Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, USA.
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Wu Y, Duan Q, Zou Y, Zhu Q, Xu Y. Discovery of novel IDO1 inhibitors targeting the protein's apo form through scaffold hopping from holo-IDO1 inhibitor. Bioorg Med Chem Lett 2021; 52:128373. [PMID: 34560264 DOI: 10.1016/j.bmcl.2021.128373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 09/13/2021] [Accepted: 09/15/2021] [Indexed: 12/23/2022]
Abstract
Immunomodulating enzyme IDO1 plays an important role in tumor immune resistance. Inhibiting IDO1 by small molecules with new mechanism of action is a potential strategy in IDO1 inhibitor development. Based on our urea derived compound originally binding with holo-IDO1, through scaffold hopping, a series of diisobutylaminophenyl hydroxyamidine compounds were designed. Unexpectedly, this novel class of IDO1 inhibitor does not target the holo form of IDO1 protein but displaces heme and binds to its apo form. Representative compound I-4 exhibits moderate potency with IC50 value of 0.44 μM in cell-based IDO1 assay, which has the potential to be developed for IDO1-related cancer treatment.
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Affiliation(s)
- Yunze Wu
- Jiangsu Key Laboratory of Drug Design and Optimization, Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, PR China
| | - Qizhu Duan
- Jiangsu Key Laboratory of Drug Design and Optimization, Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, PR China
| | - Yi Zou
- Jiangsu Key Laboratory of Drug Design and Optimization, Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, PR China
| | - Qihua Zhu
- Jiangsu Key Laboratory of Drug Design and Optimization, Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, PR China
| | - Yungen Xu
- Jiangsu Key Laboratory of Drug Design and Optimization, Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, PR China.
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Kassab SE, Mowafy S. Structural Basis of Selective Human Indoleamine-2,3-dioxygenase 1 (hIDO1) Inhibition. ChemMedChem 2021; 16:3149-3164. [PMID: 34174026 DOI: 10.1002/cmdc.202100253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 06/23/2021] [Indexed: 11/08/2022]
Abstract
hIDO1 is a heme-dioxygenase overexpressed in the tumor microenvironment and is implicated in the survival of cancer cells. Metabolism of tryptophan to N-formyl-kynurenine by hIDO1 leads to immune suppression to result in cancer cell immune escape. In this article, we discuss the discovery of selective hIDO1 inhibitors for therapeutic intervention that have been promoted to clinical trials and for which crystallographic structural information is available for the respective inhibitor-enzyme complex. The structural insights are based on the complex crystal structures and the relative biological data profiles. The structural basis of selective hIDO1 inhibition, as discussed herein, opens new avenues to the discovery of novel inhibitors with improved activity profiles, selectivity, and distinct structure frameworks.
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Affiliation(s)
- Shaymaa Emam Kassab
- Pharmaceutical Chemistry Department, Faculty of Pharmacy, Damanhour University, Damanhour, El-Buhaira, 22516, Egypt
| | - Samar Mowafy
- Pharmaceutical Chemistry Department, Faculty of Pharmacy, Misr International University, Cairo, 11431, Egypt.,Department of Chemistry, University of Washington, Seattle, Washington, 98195, United States of America
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Kim M, Tomek P. Tryptophan: A Rheostat of Cancer Immune Escape Mediated by Immunosuppressive Enzymes IDO1 and TDO. Front Immunol 2021; 12:636081. [PMID: 33708223 PMCID: PMC7940516 DOI: 10.3389/fimmu.2021.636081] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/04/2021] [Indexed: 12/24/2022] Open
Abstract
Blockade of the immunosuppressive tryptophan catabolism mediated by indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO) holds enormous promise for sensitising cancer patients to immune checkpoint blockade. Yet, only IDO1 inhibitors had entered clinical trials so far, and those agents have generated disappointing clinical results. Improved understanding of molecular mechanisms involved in the immune-regulatory function of the tryptophan catabolism is likely to optimise therapeutic strategies to block this pathway. The immunosuppressive role of tryptophan metabolite kynurenine is becoming increasingly clear, but it remains a mystery if tryptophan exerts functions beyond serving as a precursor for kynurenine. Here we hypothesise that tryptophan acts as a rheostat of kynurenine-mediated immunosuppression by competing with kynurenine for entry into immune T-cells through the amino acid transporter called System L. This hypothesis stems from the observations that elevated tryptophan levels in TDO-knockout mice relieve immunosuppression instigated by IDO1, and that the vacancy of System L transporter modulates kynurenine entry into CD4+ T-cells. This hypothesis has two potential therapeutic implications. Firstly, potent TDO inhibitors are expected to indirectly inhibit IDO1 hence development of TDO-selective inhibitors appears advantageous compared to IDO1-selective and dual IDO1/TDO inhibitors. Secondly, oral supplementation with System L substrates such as leucine represents a novel potential therapeutic modality to restrain the immunosuppressive kynurenine and restore anti-tumour immunity.
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Affiliation(s)
- Minah Kim
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Petr Tomek
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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