Metabolite Of Retinol Research Articles

Molecular Interactions of Selective Agonists and Antagonists with the Retinoic Acid Receptor γ.

All-trans retinoic acid (ATRA), the major active metabolite of all-trans retinol (vitamin A), is a key hormonal signaling molecule. In the adult organism, ATRA has a widespread influence on processes that are crucial to the growth and differentiation of cells and, in turn, the acquisition of mature cell functions. Therefore, there is considerable potential in the use of retinoids to treat diseases. ATRA binds to the retinoic acid receptors (RAR) which, as activated by ATRA, selectively regulate gene expression. There are three main RAR isoforms, RARα, RARβ, and RARγ. They each have a distinct role, for example, RARα and RARγ regulate myeloid progenitor cell differentiation and hematopoietic stem cell maintenance, respectively. Hence, targeting an isoform is crucial to developing retinoid-based therapeutics. In principle, this is exemplified when ATRA is used to treat acute promyelocytic leukemia (PML) and target RARα within PML-RARα oncogenic fusion protein. ATRA with arsenic trioxide has provided a cure for the once highly fatal leukemia. Recent in vitro and in vivo studies of RARγ have revealed the potential use of agonists and antagonists to treat diseases as diverse as cancer, heterotopic ossification, psoriasis, and acne. During the final drug development there may be a need to design newer compounds with added modifications to improve solubility, pharmacokinetics, or potency. At the same time, it is important to retain isotype specificity and activity. Examination of the molecular interactions between RARγ agonists and the ligand binding domain of RARγ has revealed aspects to ligand binding that are crucial to RARγ selectivity and compound activity and key to designing newer compounds.

Oral isotretinoin induced giant lobular capillary haemangioma over scalp: a rare case report

With the advent of isotretinoin in the last 2 decades, dermatotheraputics has reached a major milestone especially in treating moderate to severe acne. Oral isotretinoin is an isomer of all-trans retinoic acid and a metabolite of retinol (vitamin A). In addition to its excellent response in moderate to severe acne, there are a number of well-documented side effects related to the use of isotretinoin. Lobular capillary haemangioma is a very rare side effect. It is sometimes known as granuloma pyogenicum and it is an acquired, benign vascular tumor that arises in tissues such as the skin and mucous membranes. Herein, we report a case of isotretinoin-induced lobular capillary hemangioma over the scalp (an atypical site).

Transcriptome-based approach to identify mechanisms underlying locomotor abnormality induced by decabromodiphenyl ethane in zebrafish larvae

The brominated flame retardant decabromodiphenyl ethane (DBDPE) has been extensively used following restrictions on BDE-209 and thus, been frequently detected in aquatic environment. However, information on impact of DBDPE on fish development and the potential mechanisms remains scarce. In present study, developing zebrafish were employed as a study model. Embryos were exposed until 5 d to DBDPE at concentrations of 0, 3, 30, and 300 μg/L, following which the impact on larval development was investigated. DBDPE bioaccumulation and locomotor hyperactivity were observed in developing zebrafish exposed to DBDPE. Transcriptome and bioinformatics analyses indicated that pathways associated with cardiac muscle contraction and retinol metabolism were notably affected. The mechanisms of DBDPE to induce locomotor abnormality were further investigated by analyzing levels of retinol and retinol metabolites, eye and heart histology, heart rates, and ATPase activity. Our results indicate that locomotor hyperactivity observed in larvae exposed to DBDPE results from abnormal heartbeat, which in turn is attributable to inhibition of Na+/K+-ATPase activity. Furthermore, DBDPE did not change larval eye histology and contents of retinoid (retinol, retinal, and retinoic acid). This study provides insight into the mechanisms underlying DBDPE-induced developmental toxicity and highlights the need for addressing the environmental risks for aquatic organisms.

Retinoic acid, RARs and early development

Vitamin A (retinol) is an important nutrient for embryonic development and adult health. Early studies identified retinoic acid (RA) as a metabolite of retinol, however, its importance was not apparent. Later, it was observed that RA treatment of vertebrate embryos had teratogenic effects on limb development. Subsequently, the discovery of nuclear RA receptors (RARs) revealed that RA controls gene expression directly at the transcriptional level through a process referred to as RA signaling. This important discovery led to further studies demonstrating that RA and RARs are required for normal embryonic development. The determination of RA function during normal development has been challenging as RA gain-of-function studies often lead to conclusions about normal development that conflict with RAR or RA loss-of-function studies. However, genetic loss-of-function studies have identified direct target genes of endogenous RA/RAR that are required for normal development of specific tissues. Thus, genetic loss-of-function studies that eliminate RARs or RA-generating enzymes have been instrumental in revealing that RA signaling is required for normal early development of many organs and tissues, including the hindbrain, posterior body axis, somites, spinal cord, forelimbs, heart, and eye.

Causal association of diet-derived circulating antioxidants with the risk of rheumatoid arthritis: A Mendelian randomization study

BackgroundAntioxidants, as scavengers of free radicals, have been proposed as potential targets for the prevention and treatment of rheumatoid arthritis (RA), however, the causal associations between antioxidants and RA are still in debate. ObjectiveThis study aims to evaluate this causal association with two-sample Mendelian randomization (MR) analysis. MethodsInverse-variance weighted was used as the major analysis method of MR. Genetic variants associated with dietary antioxidants including vitamin E (α- and γ-tocopherol), β-carotene, lycopene, vitamin C (L-ascorbic acid or ascorbate), and retinol, and their circulating metabolites were used as instrumental variables. The causal effects of the antioxidants were assessed in genome-wide association study datasets of RA from a previous publication (Okada Y. et al.) and Finngen consortium and combined with meta-analysis. ResultsWe observed that the levels of circulating retinol metabolite negatively correlates with the risk of overall RA in the dataset from Okada Y. et al. (odds ratio [OR]=0.952, 95% confidence interval [CI]=0.911−0.996, p = 0.031) and Finngen (OR=0.946, 95%CI=0.903−0.991, p = 0.020). The causal association remained consistent in the meta-analysis (OR=0.949, 95%CI=0.919−0.98, p = 0.002). Increased levels of circulating retinol metabolite also suggestively decreased the risk of seropositive RA (OR=0.936, 95%CI=0.884−0.992, p = 0.025) but not seronegative RA (OR=0.996, 95%CI=0.921−1.076, p = 0.913). No causal effects of other dietary antioxidants on RA were identified in our analyses. ConclusionsOur study suggested a protective effect of circulating retinol metabolites, but not other antioxidants, on overall RA and seropositive RA. Dietary supplementation of retinol may be an effective measure for the primary prevention of RA.

Plasma Retinoid Concentrations Are Altered in Pregnant Women.

Vitamin A is vital to maternal–fetal health and pregnancy outcomes. However, little is known about pregnancy associated changes in maternal vitamin A homeostasis and concentrations of circulating retinol metabolites. The goal of this study was to characterize retinoid concentrations in healthy women (n = 23) during two stages of pregnancy (25–28 weeks gestation and 28–32 weeks gestation) as compared to ≥3 months postpartum. It was hypothesized that plasma retinol, retinol binding protein 4 (RBP4), transthyretin and albumin concentrations would decline during pregnancy and return to baseline by 3 months postpartum. At 25–28 weeks gestation, plasma retinol (−27%), 4-oxo-13-cis-retinoic acid (−34%), and albumin (−22%) concentrations were significantly lower, and all-trans-retinoic acid (+48%) concentrations were significantly higher compared to ≥3 months postpartum in healthy women. In addition, at 28–32 weeks gestation, plasma retinol (−41%), retinol binding protein 4 (RBP4; −17%), transthyretin (TTR; −21%), albumin (−26%), 13-cis-retinoic acid (−23%) and 4-oxo-13-cis-retinoic acid (−48%) concentrations were significantly lower, whereas plasma all-trans-retinoic acid concentrations (+30%) were significantly higher than ≥3 months postpartum. Collectively, the data demonstrates that in healthy pregnancies, retinol plasma concentrations are lower, but all-trans-retinoic acid concentrations are higher than postpartum.

Association between Circulating Antioxidants and Longevity: Insight from Mendelian Randomization Study.

Background Antioxidants attracted long-standing attention as promising preventive agents worldwide. Previous observational studies have reported that circulating antioxidants are associated with reduced mortality; however, randomized clinical trials indicate neutral or harmful impacts. The association of long-term circulating antioxidant exposure with longevity is still unclear. Objectives We aim to determine whether long-term circulating antioxidant exposure is causally associated with longevity in the general population using the two-sample Mendelian randomization (MR) design. Methods Genetic instruments for circulating antioxidants (ascorbate, lycopene, selenium, beta-carotene, and retinol) and antioxidant metabolites (ascorbate, alpha-tocopherol, gamma-tocopherol, and retinol) were identified from the largest up-to-date genome-wide association studies (GWASs). Summary statistics of these instruments with individual survival to the 90th vs. 60th percentile age (11,262 cases and 25,483 controls) and parental lifespan (N = 1,012,240 individuals) were extracted. The causal effect was estimated using the inverse-variance weighted method in the main analysis and complemented by multiple sensitivity analyses to test the robustness of results. Results We found that genetically determined higher concentration of circulating retinol (vitamin A) metabolite was casually associated with a higher odds of longevity (OR, 1.07; 95% CI, 1.02–1.13; P < 0.01) and increased parental lifespan (lifespan years per 10-fold increase: 0.17; 95% CI, 0.07–0.27; P < 0.01). Present evidence did not support a causal impact of circulating ascorbate (vitamin C), tocopherol (vitamin E), lycopene, selenium or beta-carotene on life expectancy. No evidence was identified to show the pleiotropic effects had biased the results. Conclusions Long-term higher exposure to retinol metabolite is causally associated with longevity in the general population. Future MR analyses could assess the current findings further by utilizing additional genetic variants and greater samples from large-scale GWASs.

Changes in the content and antioxidative activity of β‐carotene and its metabolite vitamin A during gastrointestinal digestion and absorption and optimisation of HPLC‐based detection

SummaryThe β‐Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat‐soluble and has low bioavailability. In previous in‐vitro assays evaluating antioxidant and 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco‐2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high‐performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results.

Identification of Indicators for Preterm Birth Using Retinoid Metabolites.

Metabolites reflect the biochemical dynamics for the maintenance of pregnancy and parturition. UPLC-Q/TOF-MS and LC-MS/MS metabolomics were performed to identify and validate the plasma metabolomic signatures of preterm birth (PTB). We recruited pregnant women between 16 and 40 weeks 5 days gestational age at Ewha Womans Mokdong Hospital for a nested case-control study. In untargeted UPLC-Q/TOF-MS, score plots of partial least-squares discriminant analysis clearly separated the PTB group from the term birth (TB, n = 10; PTB, n = 11). Fifteen metabolites were significantly different between the two groups, as indicated by a variable importance in projection >1 and p < 0.05. Metabolic pathways involving retinol, linoleic acid, d-arginine, and d-ornithine were associated with PTB. Verification by LC-MS/MS focused on retinol metabolism (TB, n = 39; PTB, n = 20). Retinol levels were significantly reduced in PTB compared to TB, while retinal palmitate, all-trans-retinal, and 13-cis-retinoic acid (13cis-RA) significantly increased (p < 0.05). Retinol-binding protein levels were also elevated in PTB. Additionally, all-trans-retinal (AUC 0.808, 95% CI: 0.683–0.933) and 13cis-RA (AUC 0.826, 95% CI: 0.723–0.930) showed improved predictions for PTB-related retinol metabolites. This study suggests that retinoid metabolism improves the accuracy of PTB predictions and plays an important role in maintaining pregnancy and inducing early parturition.

Abstract 4658: Association of serum retinol with risk of overall and cause-specific mortality: A 30-year prospective cohort study

Abstract Retinoic acid, an active metabolite of retinol, has been associated with increased overall and cardiovascular mortality. However, the association between retinol, the most biologically active vitamin A metabolite, and long-term mortality is unexplored. The objective of this study is to determine whether serum retinol is associated with overall and cause-specific mortality, and to elucidate the dose-response characteristics of the association. We conducted a prospective serological analysis of 29,104 men in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study cohort. Serum retinol was assayed at baseline using high-performance liquid chromatography, and multivariable-adjusted Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and their two-sided 95% confidence intervals (CIs). During a 30-year follow-up through linkage with Finnish Causes of Death Registry, there were 23,797 deaths, including from cardiovascular disease (9,869), cancer (7,695), respiratory disease (2,161), diabetes mellitus (119), injuries and accidents (1,255), and other causes (2698). In the multivariable-adjusted model, participants with higher serum retinol experienced significantly lower overall mortality compared to men with the lowest concentrations (HRs=0.87, 0.84, 0.80 and 0.83 for quintile 2 (Q2)-Q5 versus Q1, respectively; Ptrend&amp;lt;0.0001). After excluding the first 5 years of follow-up following blood collection, the associations were generally similar, with higher serum retinol being significantly associated with reduced overall mortality, as well as mortality from cardiovascular disease, heart disease, respiratory disease and other causes (reductions of risk from 15% to 32% for the highest versus lowest retinol quintiles). By contrast, the serum retinol associations with cancer and stroke mortality were not significant after excluding the first 5 years (HRs=0.91 and 0.89, Q5 versus Q1; Ptrend=0.09 and 0.21, respectively). The retinol-total mortality association was similar across subgroups of age, smoking intensity and duration, BMI, trial supplementation and duration of follow-up, but was modified by alcohol consumption, with a stronger inverse association among men who drank more (≥20.4 g/day; HRs= 0.82. 0.75, 0.74. 0.74, Q2-Q5 versus Q1, respectively; Pinteraction=0.002). In this large prospective cohort analysis, high serum retinol is associated with lower overall mortality, including deaths from cardiovascular disease, heart disease, respiratory disease and other causes. Our data provide evidence of the importance of vitamin A biochemical status for long-term health. Citation Format: Jiaqi Huang, Stephanie J. Weinstein, Kai Yu, Demetrius Albanes. Association of serum retinol with risk of overall and cause-specific mortality: A 30-year prospective cohort study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4658.

The Systemic Metabolic Profile Early after Allogeneic Stem Cell Transplantation: Effects of Adequate Energy Support Administered through Enteral Feeding Tube.

Patients undergoing allogeneic stem cell transplantation usually require nutritional support. There is no consensus on whether enteral support through tube feeding should be preferred. A recent randomized study could not detect any difference between enteral and parenteral feeding with regard to post-transplant outcomes, whereas 2 retrospective studies described an association between enteral feeding and a favorable post-transplant outcome. We compared pre- and post-transplant plasma metabolomic profiles for 10 patients receiving mainly enteral nutritional support and 10 patients receiving mainly parenteral support. Samples were collected before conditioning and 3 weeks post-transplant; 824 metabolites were analyzed using mass spectrometry. The pretransplant metabolite profiles showed a significant overlap between the 2 groups. Post-transplant samples for both patient groups showed an increase of secondary bile acids and endocannabinoids, whereas reduced levels were seen for food preservatives, plasmalogens, and retinol metabolites. The main post-transplant differences between the groups were decreased levels of fatty acids and markers of mitochondrial activation in the control group, indicating that these patients had insufficient energy intake. A significant effect was also seen for heme/bilirubin metabolism for the parenteral support. To conclude, allotransplant recipients showed altered metabolic profiles early after transplantation; this was mainly due to the conditioning/transplantation/reconstitution, whereas the type of nutritional support had minor effects.

Retinoic acid signaling pathways

Retinoic acid (RA), a metabolite of retinol (vitamin A), functions as a ligand for nuclear RA receptors (RARs) that regulate development of chordate animals. RA-RARs can activate or repress transcription of key developmental genes. Genetic studies in mouse and zebrafish embryos that are deficient in RA-generating enzymes or RARs have been instrumental in identifying RA functions, revealing that RA signaling regulates development of many organs and tissues, including the body axis, spinal cord, forelimbs, heart, eye and reproductive tract. An understanding of the normal functions of RA signaling during development will guide efforts for use of RA as a therapeutic agent to improve human health. Here, we provide an overview of RA signaling and highlight its key functions during development.

Raldh1 promotes adiposity during adolescence independently of retinal signaling.

All-trans-retinoic acid (RA) inhibits adipogenesis in established preadipocyte cell lines. Dosing pharmacological amounts of RA reduces weight gain in mice fed a high-fat diet, i.e. counteracts diet-induced obesity (DIO). The aldehyde dehydrogenase Raldh1 (Aldh1a1) functions as one of three enzymes that converts the retinol metabolite retinal into RA, and one of many proteins that contribute to RA homeostasis. Female Raldh1-ablated mice resist DIO. This phenotype contrasts with ablations of other enzymes and binding-proteins that maintain RA homeostasis, which gain adiposity. The phenotype observed prompted the conclusion that loss of Raldh1 causes an increase in adipose tissue retinal, and therefore, retinal functions independently of RA to prevent DIO. A second deduction proposed that low nM concentrations of RA stimulate adipogenesis, in contrast to higher concentrations. Using peer-reviewed LC/MS/MS assays developed and validated for quantifying tissue RA and retinal, we show that endogenous retinal and RA concentrations in adipose tissues from Raldh1-null mice do not correlate with the phenotype. Moreover, male Raldh1-null mice resist weight gain regardless of dietary fat content. Resistance to weight gain occurs during adolescence in both sexes. We show that RA concentrations as low as 1 nM, i.e. in the sub-physiological range, impair adipogenesis of embryonic fibroblasts from wild-type mice. Embryonic fibroblasts from Raldh1-null mice resist differentiating into adipocytes, but retain ability to generate RA. These fibroblasts remain sensitive to an RA receptor pan-agonist, and are not affected by an RA receptor pan-antagonist. Thus, the data do not support the hypothesis that retinal itself represses weight gain and adipogenesis independently of RA. Instead, the data indicate that Raldh1 functions as a retinal and atRA-independent promoter of adiposity during adolescence, and enhances adiposity through pre-adipocyte cell autonomous actions.

Retinoic acid induces hypersegmentation and enhances cytotoxicity of neutrophils against cancer cells

Hypersegmentation of nuclei is considered a distinct characteristic of the antitumoral phenotype of neutrophils. Retinoic acid, a metabolite of retinol, reorganizes and induces segmentation of the nucleus during the differentiation of neutrophils. However, the role of retinoic acid in the phenotype polarization of neutrophils has not been fully established. Here, we investigated the effect of retinoic acid on phenotype polarization of neutrophils. Retinoic acid-induced the hypersegmentation of human neutrophils via retinoic acid receptors and mTOR pathways. Retinoic acid-induced hypersegmented neutrophils enhanced neutrophil extracellular traps (NETs) formation in response to phorbol-12-myristate 13-acetate (PMA) and fMLP (N-Formylmethionine-leucyl-phenylalanine) stimulation, and increased cytotoxicity against various tumor cells. Moreover, retinoic acid treatment attenuated tumor growth in a murine model of tumor. Taken together, these results suggests that retinoic acid induces the phenotype polarization of neutrophils to exert antitumor effects.

Disruption of Retinol (Vitamin A) Signaling by Phthalate Esters: SAR and Mechanism Studies.

A spectrum of reproductive system anomalies (cryptorchidism, hypospadias, dysgenesis of Wolffian duct-derived tissues and prostate, and reduced sperm production) in male rats exposed in utero to phthalate esters (PEs) are thought to be caused by PE inhibition of fetal testosterone production. Recently, dibutyl and dipentyl phthalate (DBuP, DPnP) were shown to disrupt the retinol signaling pathway (RSP) in mouse pluripotent P19 embryonal carcinoma cells in vitro. The RSP regulates the synthesis and cellular levels of retinoic acid (RA), the active metabolite of retinol (vitamin A). In this new study, a total of 26 di- and mono-esters were screened to identify additional phthalate structures that disrupt the RSP and explore their mechanisms of action. The most potent PEs, those causing > 50% inhibition, contained aryl and cycloalkane groups or C4-C6 alkyl ester chains and were the same PEs reported to cause malformations in utero. They shared similar lipid solubility; logP values were between 4 and 6 and, except for PEs with butyl and phenyl groups, were stable for prolonged periods in culture. Mono- and cognate di-esters varied in ability to disrupt the RSP; e.g., DEHP was inactive but its monoester was active while DBuP was active yet its monoester was inactive. DBuP and dibenzyl phthalate both disrupted the synthesis of RA from retinol but not the ability of RA to activate gene transcription. Both PEs also disrupted the RSP in C3H10T1/2 multipotent mesenchymal stem cells. Based on this in vitro study showing that some PEs disrupt retinol signaling and previous in vivo studies that vitamin A/RA deficiency and PEs both cause strikingly similar anomalies in the male rat reproductive system, we propose that PE-mediated inhibition of testosterone and RA synthesis in utero are both causes of malformations in male rat offspring.

High dietary fat–induced obesity in Wistar rats and type 2 diabetes in nonobese Goto-Kakizaki rats differentially affect retinol binding protein 4 expression and vitamin A metabolism

Obesity is a major risk factor for type 2 diabetes, which is caused mainly by insulin resistance. Retinol binding protein 4 (RBP4) is the only specific transport protein for retinol in the serum. RBP4 level is increased in the diabetic state and high-fat condition, indicating that retinol metabolism may be affected under these conditions. However, the precise effect of diabetes and high fat–induced obesity on retinol metabolism is unknown. In this study, we examined differences in retinol metabolite levels in rat models of diet-induced obesity and type 2 diabetes (Goto-Kakizaki [GK] rat). Four-week-old male Wistar and GK rats were given either a control diet (AIN-93G) or a high-fat diet (HFD, 40% fat kJ). After 15 weeks of feeding, the RBP4 levels increased by 2-fold in the serum of GK rats but not HFD-fed rats. The hepatic retinol concentration of HFD-fed rats was approximately 50% that of the controls (P < .01). In contrast, the renal retinol concentrations of GK rats increased by 70% (P < .01). However, expression of RARβ in the kidney, which was induced in a retinoic acid–dependent manner, was downregulated by 90% (P < .01) in GK rats. In conclusion, diabetes and obesity affected retinol metabolism differently, and the effects were different in different peripheral tissues. The impact of HFD may be limited to the storage of hepatic vitamin A as retinyl palmitate. In particular, our data indicate that renal retinoic acid production might represent an important target for the treatment of type 2 diabetes mellitus.

Retinoic acid liposome-hydrogel: preparation, penetration through mouse skin and induction of F9 mouse teratocarcinoma stem cells differentiation

Retinoic acid (RA), a metabolite of retinol, is one of the most biologically active forms of retinoid and plays vital roles in embryonic development and in the regulation of cell proliferation and differentiation. Knowing that liposomes simulate cell membranes and that hydrogel is an ideal delivery vehicle for topical medicine, liposome-hydrogel is a novel preparation that has synergistic advantages over each component separately. Our objective was to investigate the characteristics of RA liposome-hydrogel. For quality control of the RA-loaded liposomes, we measured their morphology, particle size, Zeta-potential, and entrapment efficiency. Then we determined the viscosity of RA liposome-hydrogel. Next, the diffusion through mouse skin was explored, followed by investigation of the mRNA expression levels of Ker18, REX1, and α-FP using Q-PCR. The results showed that RA liposome-hydrogel penetrates the mouse skin effectively. The permeation rates were: Qn (%) of RA liposome-hydrogel &lt; Qn(%) of RA-loaded liposome &lt; Qn (%) of RA. The mRNA expression levels were dose-dependent and the effective dose decreased between vehicles due to their different release rates. F9 mouse teratocarcinoma stem cells were an ideal model to explore the mechanism of RA liposome-hydrogel in stem cell differentiation.

Abstract 2678: All-trans-retinoic acid as a new therapeutic approach to target isocitrate dehydrogenase mutations in acute myeloid leukemia

Abstract Mutations of isocitrate dehydrogenases 1 and 2 (IDH1/2) occur in about 15% of acute myeloid leukemia (AML) patients, and lead to the production of an oncometabolite, the 2-hydroxyglutarate (2-HG). Importantly, many clinical studies demonstrated that IDH1/2 mutations are systematically conserved at relapse, suggesting that this mutated enzyme could contribute to early leukemogenesis. In an effort to identify therapy specifically targeting IDH1 R132H mutated blasts, we developed an AML cell line model carrying IDH1 R132H mutation. We first stably transduced HL60 cell line to establish clones carrying either empty vector, IDH1 WT gene or IDH1-R132H mutated gene. We then characterized these clones with different features including 2-HG production. Since demethylation of many genes involved in the retinol metabolism is impaired by IDH1-R132H mutation and because all-trans retinoic acid (ATRA), a retinol metabolite, is already used in clinic, we studied its effects on IDH1-R132H mutated AML cells. Here, we showed on our transduced models as well as on primary AML patient samples (n=6), that AML blasts harboring IDH1-R132H mutation were highly sensitive to low doses of ATRA, compared to the IDH1 WT. In fact, IDH1-R132H mutation sensitized to ATRA-induced differentiation, as shown by increased expression of the differentiation marker CD11b and morphological changes evidenced with May-Grünwald-Giemsa staining. This was followed by changes of CD14 and CD15 expression, as well as granulocytic enzymatic activity measured with the nitroblue tetrazolium reduction assay. This terminal granulocytic differentiation came with the reduction of proliferation and colony formation, and then, quickly led to apoptosis of IDH1 R132H mutated AML cells. Moreover, we showed that the level of differentiation of IDH1 R132H mutated models was correlated to the magnitude of IDH1-R132H protein expression and thus to the 2-HG production. We further demonstrated that treatment with a cell-permeable form of 2-HG sensitized empty construct to ATRA-induced differentiation, whereas the inhibition of IDH1-R132H activity reduced its ATRA-sensitivity in IDH1-R132H mutant. Altogether, our results show that IDH1-R132H mutation sensitizes to ATRA-induced granulocytic terminal differentiation in a 2-HG concentration-dependent manner and that it leads to their apoptosis. Since serum 2-HG concentration of IDH mutated patients is approximately 100 fold higher than for non mutated patient, we could expect a high and specific effect of ATRA treatment on IDH1 mutated AML patients. Furthermore, as this mutation could contribute to relapse, this might be a promising therapeutic strategy to achieve a long-term remission in AML with IDH1 mutations. Citation Format: Helena Boutzen, Fabienne De Toni, Estelle Saland, Eric Delabesse, Véronique De mas, Cécile Demur, Florence Castelli, Lara Gales, Virginie Penard-lacronique, Stéphane De Botton, Jean-Charles Portais, Christophe Junot, Stéphane Manenti, Christian Récher, Jean-emmanuel Sarry. All-trans-retinoic acid as a new therapeutic approach to target isocitrate dehydrogenase mutations in acute myeloid leukemia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2678. doi:10.1158/1538-7445.AM2014-2678

Synthesis of 11C-labeled retinoic acid, [11C]ATRA, via an alkenylboron precursor by Pd(0)-mediated rapid C-[11C]methylation

Retinoids are a class of chemical compounds which include both natural dietary vitamin A (retinol) metabolites and active synthetic analogs. Both experimental and clinical studies have revealed that retinoids regulate a wide variety of essential biological processes. In this study, we synthesized 11C-labeled all-trans-retinoic acid (ATRA), the most potent biologically active metabolite of retinol and used in the treatment of acute promyelocytic leukemia. The synthesis of 11C-labeled ATRA was accomplished by a combination of rapid Pd(0)-mediated C-[11C]methylation of the corresponding pinacol borate precursor prepared by 8 steps and hydrolysis. [11C]ATRA will prove useful as a PET imaging agent, particularly for elucidating the improved therapeutic activity of ATRA (natural retinoid) for acute promyelocytic leukemia by comparing with the corresponding PET probe [11C]Tamibarotene (artificial retinoid).

Vitamin A/retinol and maintenance of pluripotency of stem cells.

Retinol, the alcohol form of vitamin A is a key dietary component that plays a critical role in vertebrate development, cell differentiation, reproduction, vision and immune system. Natural and synthetic analogs of retinol, called retinoids, have generally been associated with the cell differentiation via retinoic acid which is the most potent metabolite of retinol. However, a direct function of retinol has not been fully investigated. New evidence has now emerged that retinol supports the self-renewal of stem cells including embryonic stem cells (ESCs), germ line stem cells (GSCs) and cancer stem cells (CSCs) by activating the endogenous machinery for self-renewal by a retinoic acid independent mechanism. The studies have also revealed that stem cells do not contain enzymes that are responsible for metabolizing retinol into retinoic acid. This new function of retinol may have important implications for stem cell biology which can be exploited for quantitative production of pure population of pluripotent stem cells for regenerative medicine as well as clinical applications for cancer therapeutics.