Synthetic Retinoid Am80 Research Articles

Abstract A052: Pharmacologic conversion of cancer-associated fibroblasts from a protumor phenotype to an antitumor phenotype improves the sensitivity of pancreatic cancer to immune checkpoint blockade therapy

Abstract Background/Purpose: Cancer-associated fibroblasts (CAFs) are one of the major cell subsets in the tumor microenvironment. Their proliferation is observed in almost all invasive cancers but is most prominent in aggressive cancers with marked desmoplastic stromal reactions, such as pancreatic ductal adenocarcinoma (PDAC). Recent single-cell transcriptomic analyses have revealed CAF heterogeneity. One approach to classify CAFs is based on their cellular roles in cancer progression: cancer-promoting CAFs (pCAFs) and cancer-restraining CAFs (rCAFs). We previously identified the glycosylphosphatidylinositol-anchored protein Meflin as a rCAF-specific marker and showed that Meflin-positive CAFs are converted into Meflin-negative CAFs during cancer progression by cell lineage experiments. Interestingly, another previous study demonstrated that the number of Meflin+ rCAFs positively correlated with the response to immune checkpoint blockade (ICB) therapy in patients with non-small cell lung cancer (NSCLC). This was also shown in mouse models, where tumors developed in Meflin KO mice and mice that overexpress Meflin showed lower and higher sensitivity to anti-PD1 antibody treatment, respectively. These data suggest the significance of the balance between pCAFs and rCAFs in ICB therapy, being consistent with recent studies that have shown the critical role of CAFs in anti-tumor immunity So, The aim of this study is to establish the effects of strategies to increase the number of rCAFs on the sensitivity to ICB therapy in PDAC. Material/Methods: A search for chemical compounds that upregulate Meflin expression was performed. We then investigated the effect of the compound on the efficacy of anti-PD-L1 antibody treatment using mouse murine models of PDAC. We also addressed the mechanism by which Meflin+ rCAFs shape the immune tumor microenvironment that potentiates the efficacy of ICB therapy. Results: We performed a chemical library screen for compounds that convert protumor CAFs into rCAFs by inducing Meflin expression. As a result, they identified the synthetic retinoid AM80 as a candidate drug that achieves that CAF conversion. Next, we observed that the induction of a Meflin-positive CAF subset with a cancer-suppressive role through the oral administration of Am80 improves intratumoral delivery and efficacy of anti-PD-L1 antibody treatment in pancreatic cancer models. Interestingly, Am80 exerted this effect when administered to tumors prior to, but not concomitant with, anti-PD-L1 antibody in wild-type but not Meflin-deficient mice. Meflin+ rCAFs induced polarization of macrophages to the M1-like phenotype and durable anti-PD-L1 treatment-mediated anti-tumor responses. Conclusion: Our data suggest that strategy of pharmacologic conversion of CAF from protumor phenotype to an antitumor phenotype CAF can improves the sensitivity of pancreatic cancer to ICB therapy. Citation Format: Tadashi Iida, Owaki Takayuki, Kota Uetsuki, Yamao Kentaro, Yasuyuki Mizutani, Takuya Ishikawa, Atsushi Enomoto, Hiroki Kawashima. Pharmacologic conversion of cancer-associated fibroblasts from a protumor phenotype to an antitumor phenotype improves the sensitivity of pancreatic cancer to immune checkpoint blockade therapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A052.

Intracellular Drug Delivery Process of Am80-Encapsulated Lipid Nanoparticles Aiming for Alveolar Regeneration.

Chronic obstructive pulmonary disease (COPD) results in obstructive ventilatory impairment caused by emphysema, and current treatment is limited to symptomatic therapy or lung transplantation. Therefore, the development of new treatments to repair alveolar destruction is especially urgent. Our previous study revealed that 1.0 mg/kg of synthetic retinoid Am80 had a repair effect on collapsed alveoli in a mouse model of elastase-induced emphysema. From these results, however, the clinical dose calculated in accordance with FDA guidance is estimated to be 5.0 mg/60 kg, and it is desirable to further reduce the dose to allow the formulation of a powder inhaler for clinical application. To efficiently deliver Am80 to the retinoic acid receptor in the cell nucleus, which is the site of action, we focused on SS-cleavable proton-activated lipid-like material O-Phentyl-P4C2COATSOME®SS-OP, hereinafter referred to as "SS-OP"). In this study, we investigated the cellular uptake and intracellular drug delivery process of Am80-encapsulated SS-OP nanoparticles to elucidate the mechanism of Am80 by nanoparticulation. Am80-encapsulated SS-OP nanoparticles were taken up into the cells via ApoE, and then Am80 was efficiently delivered into the nucleus via RARα. These results indicated the usefulness of SS-OP nanoparticles as drug delivery system carriers of Am80 for COPD treatment.

Venous Thromboembolism in Patients with Steroid-Refractory Chronic Graft-Versus-Host Disease Receiving Synthetic Retinoid Am80

Chronic graft-versus-host disease (GVHD) remains a major cause of late death and morbidity after allogeneic hematopoietic cell transplantation, and the treatment of chronic GVHD remains challenging. All-trans retinoic acid (ATRA), a potent vitamin A derivative, can regulate immune responses. Synthetic retinoid Am80, which shows biological activity approximately 10 times more potent than that of ATRA, directly inhibits Th1 cytokine production. We previously reported in an experimental mouse model that Am80 down-regulated both Th1 and Th17 differentiation in donor T cells, resulting in attenuation of chronic GVHD (Nishimori H. et al. Blood 2012). Based on this background, we conducted an open-labeled, multicenter phase II study of Am80 in patients with steroid-refractory chronic GVHD (Maeda Y. et al. Acta Med. Okayama. 2016). Six facilities are participating in this study. Patients take Am80 orally (4 mg/day) for 24 weeks. If any unexpected adverse events with Grade 2 or expected adverse events with Grade 3 develop, the daily dose will be decreased to 2 mg/day, 2 mg every other day, or discontinued.Eighteen patients were enrolled and 5 out of 18 (27.8%) patients experienced venous thromboembolism (VTE). Table 1 shows the patient characteristics of those developed VTEs.It is controversial whether retinoid would enhance the incidence of VTE. Only one patient reported thrombosis when Am80 orally (6 mg/m2) for 2-8 weeks was administrated to approximately 800 patients with acute promyelocytic leukemia. In this study, 5 out of 18 (27.8%) patients experienced thrombosis and the safety committee in this study has stopped the trial due to safety concerns. Recently, a meta-analysis reported the incidence of VTE in chronic GVHD was 35 % (20-54 %). Further studies are needed to confirm the causal relationship between Am80 orally (4 mg/day) for 24 weeks and VTE. And also, alternative treatment schedule in addition to anticoagulants for the prevention of VTE will be investigated in subsequent studies. [Display omitted] DisclosuresNishimori:Toko Pharmaceutical Industries: Other: Investigational drug is provided free of charge.. Maeda:Toko Pharmaceutical Industries: Other: Investigational drug is provided free of charge.

Synthetic retinoid AM80 inhibits IL‐17 production of gamma delta T cells and ameliorates biliary atresia in mice

AbstractBackground & AimsRecent evidence suggests that Interleukin (IL)‐17‐producing gamma delta () T cells are the dominant pathogenic cellular component in designated autoimmune or inflammatory diseases, including biliary atresia (BA). We have previously demonstrated that retinoids effectively suppress T‐helper cell (Th) 17 differentiation.MethodsHere, we established an in vitro system, enabling investigations of the effect of AM80 on the IL‐17 production of T cells. Additionally, we tested the therapeutic effect of AM80 in the Rotavirus‐induced mouse model of BA. Co‐incubation of T cells with IL‐23 and anti‐CD28 mAb proved most effective in inducing an IL‐17 response in vitro. The effect of AM80 on human CCR6+CD26+ V2 cells was assessed by flow cytometry.ResultsAM80 efficiently reduced IL‐17 production by murine T cells and the expression of the master transcription factor Retinoid‐Orphan‐Receptor‐t (ROR) in a dose‐dependent manner. The fraction of human CCR6+CD26+ V2 cells was significantly reduced by co‐incubation with AM80. Moreover, AM80 also inhibited IL‐17 production by liver‐infiltrating T cells isolated from animals suffering from BA. Intraperitoneal treatment with AM80 ameliorated BA‐associated inflammation. However, AM80 treatment was not sufficient to control disease progression in the murine model, despite reduced inflammatory activity in the animals.ConclusionsRetinoids are very efficient in down‐regulating IL‐17 production by T cells in vitro and, to a lesser extent, in the BA mouse model. However, retinoids do not suffice for the control of disease progression. Thus, our data suggest that IL‐17 is not the only factor contributing to the pathogenesis of BA.Lay summaryBiliary atresia (BA) is a rare disease which affects infants, causing progressive liver failure in most children, and is the most common indication for paediatric liver transplantation. We have previously demonstrated that IL‐17, produced by T cells, contributes to hepatic inflammation in the murine model of BA and is increased in the livers of infants suffering from the disease. In the study at hand, we demonstrate that treatment with AM80, a synthetic retinoid with superior pharmacological properties, effectively inhibits the IL‐17 production of gamma delta T cells without generating systemic immunosuppression. Although all‐trans retinoic acid (ATRA) has been demonstrated to suppress differentiation of IL‐17‐producing conventional T‐helper cells (Th17) in vitro, the therapeutic application of ATRA in vivo is limited by the compound's potential side effects caused by its instability and lack of receptor specificity. Our study is the first to show that AM80 suppresses the IL‐17 production of T cells in a very efficient manner and that hepatic inflammation is ameliorated in mice suffering from BA. However, AM80 treatment does not suffice to block the disease progression. We conclude that factors other than IL‐17 drive the progressive inflammation in BA. The addition of retinoids to the treatment regime of children suffering from BA might decrease the disease burden; however, further research is needed to clarify the pathomechanism and possible therapeutic interventions in humans.

Synthetic Retinoid AM80 Ameliorates Lung and Arthritic Autoimmune Responses by Inhibiting T Follicular Helper and Th17 Cell Responses.

Rheumatoid arthritis is an autoimmune disorder that affects the joints and other organs. Pulmonary complications contribute significantly to rheumatoid arthritis mortality. Retinoic acid and its synthetic compound AM80 play roles in immunoregulation but their effect on mucosal autoimmunity remains largely unknown. T follicular helper (Tfh) and Th17 cells are known to promote inflammation and autoantibody production. Using the K/BxN autoimmune arthritis model, we elucidate a novel mechanism whereby oral AM80 administration suppressed lung mucosa-associated Tfh and autoantibody responses by increasing the gut-homing α4β7 integrin expression on Tfh cells. This diverted Tfh cells from systemic (non-gut) inflamed sites such as the lung into the gut-associated lymphoid tissues, Peyer's patches, and thus reduced the systemic autoantibodies. AM80 also inhibited the lung Th17 response. AM80's effect in the lungs was readily applied to the joints as AM80 also inhibited Tfh and Th17 responses in the spleen, the major autoantibody producing site known to correlate with K/BxN arthritis severity. Finally, we used anti-β7 treatment as an alternative approach, demonstrating that manipulating T cell migration between the gut and systemic sites alters the systemic disease outcome. The β7 blockade prevented both Tfh and Th17 cells from entering the non-immunopathogenic site, the gut, and retained these T effector cells in the systemic sites, leading to augmented arthritis. These data suggest a dual beneficial effect of AM80, targeting both Tfh and Th17 cells, and warrant strict safety monitoring of gut-homing perturbing agents used in treating intestinal inflammation.

Abstract 4723: Innovative cancer treatment of human lung cancer cells PC-9 with a synthetic retinoid Am80 and EGCG via inhibition of HDAC4 and HDAC5

Abstract A synthetic new retinoid Am80 (tamibarotene) is used for treatment of acute promyelocytic leukemia (APL) patients with resistance of all-trans-retinoic acid (ATRA). To potentiate efficacy of Am80, we challenged combination treatment of Am80 and EGCG on human lung cancer cell line PC-9. It is now well accepted that EGCG acts as synergist with numerous anticancer compounds, and that the average reduction of tumor volume for in vivo genograft mouse models implanted using various human cancer cell lines was 70.3% with combinations of 13 anticancer compounds and EGCG. We previously reported that combinations of NSAIDs (sulindac and celecoxib) or other retinoids (ATRA, 13-cis-RA and 9-cis-RA) and EGCG synergistically induced apoptosis of the cells along with strong expression of growth arrest and DNA-damage inducible gene 153 (GADD153) and death receptor (DR5) gene. Our objective was to investigate the mechanism of the synergistic induction for GADD153-DR5 apoptosis pathway. The proteomic analysis of lysine-acetylated proteins was conducted with a shotgun analysis using nanoLC-ESI-MS/MS in PC-9 cells. We found that the numbers of acetylated proteins were different: 551 acetylated proteins were found in non-treated cells, 331 proteins in cells treated with combination, and 59 proteins were common in both cases. Acetylation was mainly found in non-histone proteins, chaperons, transcription factors, and enzymes. The combination increased acetylated p53 (Lys382) about 3-fold compared with non-treated cells. In addition, combination significantly decreased the protein amounts of histone deacetylase (HDAC) 4 and HDAC 5 to 50% and 20%, respectively, but not HDAC6 among Class II HDACs. Class I HDACs (HDAC1, 2, and 3) were not decreased. All the results suggest that combination of Am80 and EGCG induces GADD153-DR5 apoptotic pathway, and reduces the amounts of HDAC4 and HDAC5 resulting in changing protein acetylation. Citation Format: Masami Suganuma, Yukiko Oya, Sonthaya Umsumarng, Keisuke Iida, Anchalee Rawangkhan, Ryo Sakai, Hiroyuki Kagechika, Koichi Shudo, Hirota Fujiki. Innovative cancer treatment of human lung cancer cells PC-9 with a synthetic retinoid Am80 and EGCG via inhibition of HDAC4 and HDAC5. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4723.

Programmed death-1 pathway in host tissues ameliorates Th17/Th1-mediated experimental chronic graft-versus-host disease.

Chronic graft-versus-host disease (GVHD) is a major cause of late death and morbidity after allogeneic hematopoietic cell transplantation, but its pathogenesis remains unclear. We investigated the role of the programmed death-1 (PD-1) pathway in chronic GVHD using a well-defined mouse model of B10.D2 (H-2(d)) donor to BALB/c (H-2(d)) recipients. PD-1 expression on allogeneic donor T cells was upregulated continuously in chronic GVHD development, whereas PD-L1 expression in host tissues was transiently upregulated and declined to basal levels in the late posttransplant period. Blockade of the PD-1 pathway by anti-PD-1, anti-PD-L1, or anti-PD-L2 mAbs exacerbated clinical and pathologic chronic GVHD. Chimeric mice revealed that PD-L1 expression in host tissues suppressed expansion of IL-17(+)IFN-γ(+) T cells, and that PD-L1 expression on hematopoietic cells plays a role in the development of regulatory T cells only during the early transplantation period but does not affect the severity of chronic GVHD. Administration of the synthetic retinoid Am80 overcame the IL-17(+)IFN-γ(+) T cell expansion caused by PD-L1 deficiency, resulting in reduced chronic GVHD damage in PD-L1(-/-) recipients. Stimulation of the PD-1 pathway also alleviated chronic GVHD. These results suggest that the PD-1 pathway contributes to the suppression of Th17/Th1-mediated chronic GVHD and may represent a new target for the prevention or treatment of chronic GVHD.

The synthetic retinoid Am80 delays recovery in a model of multiple sclerosis by modulating myeloid-derived suppressor cell fate and viability

Relapsing–remitting multiple sclerosis (RR-MS) is an inflammatory and demyelinating disease of the central nervous system (CNS). It is characterized by relapsing phases with ongoing neurological affectation that are followed by a remitting period in which inflammatory events are controlled and the patients partially recover. Experimental Autoimmune Encephalomyelitis (EAE) is the animal model most often used to study the inflammatory component of MS. Several cell types are involved in controlling the immune response in EAE and immature myeloid-derived suppressor cells (MDSCs) have emerged as important actors in the immunomodulation that occurs in EAE due to their ability to suppress inflammatory responses by inducing T cell apoptosis. In this study, we assessed whether MDSC differentiation may have consequences on the clinical course of EAE by treating mice around the peak of the clinical course EAE with the MDSC-differentiating agent Am80, an analogue of retinoid acid. Am80 administration abrogates the immunomodulation that occurs in EAE mice through different MDSC-related mechanisms: i) induction of MDSC apoptosis; ii) polarization of MDSCs to mature subsets of myeloid cells (dendritic cells/macrophages/neutrophils); and iii) altering their immunosuppressor phenotype. Consequently, T cell density increases and their viability is promoted, delaying the animal's recovery. Therefore, our data point to MDSC behaviour as a crucial factor in facilitating the transition from the relapsing to the remission phase in EAE, which should be considered for future immune-related therapies for MS.

Synthetic retinoid Am80 controls growth of intracellular Toxoplasma by inhibiting acquisition and synthesis of cholesterol in macrophages

Synthetic retinoid Am80 controls growth of intracellular <i>Toxoplasma</i> by inhibiting acquisition and synthesis of cholesterol in macrophages

Synthetic retinoid Am80 up-regulates apelin expression by promoting interaction of RARα with KLF5 and Sp1 in vascular smooth muscle cells

Previous studies have demonstrated that both retinoids and apelin possess potent cardiovascular properties and that retinoids can mediate the expression of many genes in the cardiovascular system. However, it is not clear whether and how retinoids regulate apelin expression in rat VSMCs (vascular smooth muscle cells). In the present study, we investigated the molecular mechanism of apelin expression regulation by the synthetic retinoid Am80 in VSMCs. The results showed that Am80 markedly up-regulated apelin mRNA and protein levels in VSMCs. Furthermore, KLF5 (Krüppel-like factor 5) and Sp1 (stimulating protein-1) co-operatively mediated Am80-induced apelin expression through their direct binding to the TCE (transforming growth factor-β control element) on the apelin promoter. Interestingly, upon Am80 stimulation, the RARα (retinoic acid receptor α) was recruited to the apelin promoter by interacting with KLF5 and Sp1 prebound to the TCE site of the apelin promoter to form a transcriptional activation complex, subsequently leading to the up-regulation of apelin expression in VSMCs. An in vivo study indicated that Am80 increased apelin expression in balloon-injured arteries of rats, consistent with the results from the cultured VSMCs. Thus the results of the present study describe a novel mechanism of apelin regulation by Am80 and further expand the network of RARα in the retinoid pathway.

Retinoic Acid Upregulates Ret and Induces Chain Migration and Population Expansion in Vagal Neural Crest Cells to Colonise the Embryonic Gut

Vagal neural crest cells (VNCCs) arise in the hindbrain, and at (avian) embryonic day (E) 1.5 commence migration through paraxial tissues to reach the foregut as chains of cells 1–2 days later. They then colonise the rest of the gut in a rostrocaudal wave. The chains of migrating cells later resolve into the ganglia of the enteric nervous system. In organ culture, E4.5 VNCCs resident in the gut (termed enteric or ENCC) which have previously encountered vagal paraxial tissues, rapidly colonised aneural gut tissue in large numbers as chains of cells. Within the same timeframe, E1.5 VNCCs not previously exposed to paraxial tissues provided very few cells that entered the gut mesenchyme, and these never formed chains, despite their ability to migrate in paraxial tissue and in conventional cell culture. Exposing VNCCs in vitro to paraxial tissue normally encountered en route to the foregut conferred enteric migratory ability. VNCC after passage through paraxial tissue developed elements of retinoic acid signalling such as Retinoic Acid Binding Protein 1 expression. The paraxial tissue's ability to promote gut colonisation was reproduced by the addition of retinoic acid, or the synthetic retinoid Am80, to VNCCs (but not to trunk NCCs) in organ culture. The retinoic acid receptor antagonist CD 2665 strongly reduced enteric colonisation by E1.5 VNCC and E4.5 ENCCs, at a concentration suggesting RARα signalling. By FACS analysis, retinoic acid application to vagal neural tube and NCCs in vitro upregulated Ret; a Glial-derived-neurotrophic-factor receptor expressed by ENCCs which is necessary for normal enteric colonisation. This shows that early VNCC, although migratory, are incapable of migrating in appropriate chains in gut mesenchyme, but can be primed for this by retinoic acid. This is the first instance of the characteristic form of NCC migration, chain migration, being attributed to the application of a morphogen.

Mechanisms of action and resistance to all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) in acute promyelocytic leukemia

Since the introduction of all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) for the treatment of acute promyelocytic leukemia (APL), the overall survival rate has improved dramatically. However, relapse/refractory patients showing resistance to ATRA and/or As2O3 are recognized as a clinically significant problem. Genetic mutations resulting in amino acid substitution in the retinoic acid receptor alpha (RARα) ligand binding domain (LBD) and the PML-B2 domain of PML-RARα, respectively, have been reported as molecular mechanisms underlying resistance to ATRA and As2O3. In the LBD mutation, ATRA binding with LBD is generally impaired, and ligand-dependent co-repressor dissociation and degradation of PML-RARα by the proteasome pathway, leading to cell differentiation, are inhibited. The PML-B2 mutation interferes with the direct binding of As2O3 with PML-B2, and PML-RARα SUMOylation with As2O3 followed by multimerization and degradation is impaired. To overcome ATRA resistance, utilization of As2O3 provides a preferable outcome, and recently, a synthetic retinoid Am80, which has a higher binding affinity with PML-RARα than ATRA, has been tested in the clinical setting. However, no strategy attempted to date has been successful in overcoming As2O3 resistance. Detailed genomic analyses using patient samples harvested repeatedly may help in predicting the prognosis, selecting the effective targeting drugs, and designing new sophisticated strategies for the treatment of APL.

Synthetic retinoid Am80 results in improved exploratory and emotional behavior in the P8 substrain of senescence-accelerated mice

Am80 is a synthetic retinoid that has been used clinically for patients with acute promyelocytic leukemia and has been reported to affect the brain and its neurons. We investigated the influence of Am80 on anti-anxiety-like behavior, which is a characteristic of age-associated emotional disorder, in the P8 strain of senescence-accelerated mice (SAMP8). Am80 at a concentration of 2mg/kg/day was administered to the mice in their feed for 1.5months. In open-field and hole-board tests, the number of ambulation, rearing, and head dipping actions, as well as the distance moved were significantly decreased in Am80-treated SAMP8 compared with untreated SAMP8. In the light/dark box test, the latencies for the first exit were significantly increased in the Am80-treated SAMP8 compared with the untreated SAMP8. Immunohistochemical analysis revealed that the area of serotonin transporter-positive immunoreactivity in the coronal sections of the forebrain of the Am80-treated SAMP8 was increased compared with the untreated SAMP8. Furthermore, the metabolic turnovers of serotonin and dopamine were increased in the amygdalae of the SAMP8 by Am80 treatment. Thus, in the present study, Am80 was found to improve exploratory and emotional behavior in SAMP8, suggesting that Am80 regulates monoamines directly or indirectly in this senescence-accelerated model.

Enhanced Lithium-Induced Brain Recovery Following Cranial Irradiation Is Not Impeded by Inflammation

Radiation-induced brain injury occurs in many patients receiving cranial radiation therapy, and these deleterious effects are most profound in younger patients. Impaired neurocognitive functions in both humans and rodents are associated with inflammation, demyelination, and neural stem cell dysfunction. Here we evaluated the utility of lithium and a synthetic retinoid receptor agonist in reducing damage in a model of brain-focused irradiation in juvenile mice. We found that lithium stimulated brain progenitor cell proliferation and differentiation following cranial irradiation while also preventing oligodendrocyte loss in the dentate gyrus of juvenile mice. In response to inflammation induced by radiation, which may have encumbered the optimal reparative action of lithium, we used the anti-inflammatory synthetic retinoid Am80 that is in clinical use in the treatment of acute promyelocytic leukemia. Although Am80 reduced the number of cyclooxygenase-2-positive microglial cells following radiation treatment, it did not enhance lithium-induced neurogenesis recovery, and this alone was not significantly different from the effect of lithium on this proinflammatory response. Similarly, lithium was superior to Am80 in supporting the restoration of new doublecortin-positive neurons following irradiation. These data suggest that lithium is superior in its restorative effects to blocking inflammation alone, at least in the case of Am80. Because lithium has been in routine clinical practice for 60 years, these preclinical studies indicate that this drug might be beneficial in reducing post-therapy late effects in patients receiving cranial radiotherapy and that blocking inflammation in this context may not be as advantageous as previously suggested.

Synthetic retinoid Am80 ameliorates chronic graft-versus-host disease by down-regulating Th1 and Th17

AbstractChronic GVHD (cGVHD) is a main cause of late death and morbidity after allogeneic hematopoietic cell transplantation, but its pathogenesis remains unclear. We investigated the roles of Th subsets in cGVHD with the use of a well-defined mouse model of cGVHD. In this model, development of cGVHD was associated with up-regulated Th1, Th2, and Th17 responses. Th1 and Th2 responses were up-regulated early after BM transplantation, followed by a subsequent up-regulation of Th17 cells. Significantly greater numbers of Th17 cells were infiltrated in the lung and liver from allogeneic recipients than those from syngeneic recipients. We then evaluated the roles of Th1 and Th17 in cGVHD with the use of IFN-γ–deficient and IL-17–deficient mice as donors. Infusion of IFN-γ−/− or IL-17−/− T cells attenuated cGVHD in the skin and salivary glands. Am80, a potent synthetic retinoid, regulated both Th1 and Th17 responses as well as TGF-β expression in the skin, resulting in an attenuation of cutaneous cGVHD. These results suggest that Th1 and Th17 contribute to the development of cGVHD and that targeting Th1 and Th17 may therefore represent a promising therapeutic strategy for preventing and treating cGVHD.

合成レチノイドAm80はTh1とTh17を抑制することにより慢性移植片対宿主病を改善する

合成レチノイドAm80はTh1とTh17を抑制することにより慢性移植片対宿主病を改善する

Oral Administration of Retinoic Acid Receptor-α/β-Specific Ligand Am80 Suppresses Experimental Autoimmune Uveoretinitis

To determine whether synthetic retinoic acid receptor (RAR)-α/β-specific agonist Am80 reduces inflammation in experimental autoimmune uveoretinitis (EAU). Naive CD4(+) T cells were activated with anti-CD3, anti-CD28, and transforming growth factor (TGF)-β, in the presence or absence of Am80. Intracellular expression of forkhead box p3 (Foxp3) and interleukin (IL)-17 in the activated CD4(+) T cells was assessed by flow cytometry. For induction of EAU, C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein (IRBP) peptide 1 to 20 (IRBP(1-20)). Am80 was administered orally every other day (3 mg/kg/time point) from day 0 to day 21. In vivo primed draining lymph node cells from vehicle-treated or Am80-treated mice were stimulated with IRBP(1-20), and culture supernatant was harvested for assay of interferon (IFN)-γ, IL-6, IL-10, and IL-17. The expression of Foxp3 and IL-6 receptor α in CD4(+) T cells of draining lymph node cells was assessed by a flow cytometer. Am80 synergized with TGF-β to induce Foxp3(+) T regulatory cells (Treg) and reciprocally inhibited development of IL-17-producing T helper cells (Th17) induced by TGF-β and IL-6. Am80 treatment reduced the severity of EAU clinically, and IFN-γ and IL-17 production was significantly reduced in Am80-treated mice. In addition, the expression of IL-6 receptor α on CD4(+) T cells was downregulated in Am80-treated mice. These findings demonstrate that Am80 treatment ameliorates severity of EAU and reduces the Th1/Th17 responses. The synthetic retinoid Am80 appears to be a promising agent for preventing autoimmune uveoretinal inflammation.

Effects of synthetic retinoid Am80 on iodide-induced autoimmune thyroiditis in nonobese diabetic mice

We examined whether a synthetic retinoid Am80 prevented the development of autoimmune thyroiditis in iodide-treated nonobese diabetic mice, an animal model of Hashimoto’s thyroiditis (HT). Am80 (0, 0.1 or 1 mg/kg/day) was orally administered in feed during the 8-week iodide treatment. While iodide ingestion effectively induced thyroiditis, Am80 administration failed to interfere with thyroiditis development and serum anti-thyroglobulin antibody levels regardless of the dose of the retinoid. Splenic T cell numbers, splenocyte proliferation and interferon-γ production were decreased in the Am80-treated mice. Our data suggest that Am80 is not a candidate for use in the prevention of HT.

Am80 inhibits stromal cell-derived factor-1-induced chemotaxis in T-cell acute lymphoblastic leukemia cells

C-X-C motif chemokine receptor 4 (CXCR4) and stromal cell-derived factor-1 (SDF-1) play a potent role in metastasis and infiltration of many types of tumors, including T-cell acute lymphoblastic leukemia (T-ALL), into the central nervous system or lymph nodes. Although higher levels of CXCR4 expression have been shown to correlate with shorter survival of patients, effective drugs affecting cell surface CXCR4 expression are still unknown. In the present study, we examined the effects of a synthetic retinoid Am80 on CXCR4 expression of cultured T-ALL cells, such as Jurkat. Am80 inhibited surface CXCR4 expression and SDF-1-induced chemotaxis by the acceleration of CXCR4 internalization via activation of conventional PKC. Am80 may be an effective drug to inhibit the extramedullary infiltration of T-ALL cells.

Oral Administration of Retinoic Acid Receptor-α/β Specific Ligand, Am80, Suppresses Experimental Autoimmune Uveoretinitis

PURPOSE To determine whether synthetic retinoic acid receptor (RAR)-α/β-specific agonist Am80 reduces inflammation in experimental autoimmune uveoretinitis (EAU). METHODS Naive CD4(+) T cells were activated with anti-CD3, anti-CD28, and transforming growth factor (TGF)-β, in the presence or absence of Am80. Intracellular expression of forkhead box p3 (Foxp3) and interleukin (IL)-17 in the activated CD4(+) T cells was assessed by flow cytometry. For induction of EAU, C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein (IRBP) peptide 1 to 20 (IRBP(1-20)). Am80 was administered orally every other day (3 mg/kg/time point) from day 0 to day 21. In vivo primed draining lymph node cells from vehicle-treated or Am80-treated mice were stimulated with IRBP(1-20), and culture supernatant was harvested for assay of interferon (IFN)-γ, IL-6, IL-10, and IL-17. The expression of Foxp3 and IL-6 receptor α in CD4(+) T cells of draining lymph node cells was assessed by a flow cytometer. RESULTS Am80 synergized with TGF-β to induce Foxp3(+) T regulatory cells (Treg) and reciprocally inhibited development of IL-17-producing T helper cells (Th17) induced by TGF-β and IL-6. Am80 treatment reduced the severity of EAU clinically, and IFN-γ and IL-17 production was significantly reduced in Am80-treated mice. In addition, the expression of IL-6 receptor α on CD4(+) T cells was downregulated in Am80-treated mice. CONCLUSIONS These findings demonstrate that Am80 treatment ameliorates severity of EAU and reduces the Th1/Th17 responses. The synthetic retinoid Am80 appears to be a promising agent for preventing autoimmune uveoretinal inflammation.