Efficacy Of All-trans Retinoic Acid Research Articles

ATRA Can Correct Impaired Proplatelet Formation By Regulating HIF-1α/SPHK2/S1P Axis in ITP

Introduction Under normal physiological conditions, the bone marrow (BM) niche is hypoxic, and sustained and consistent oxygen gradients result in stable physiological hypoxia. Hypoxia inducible factor (HIF) is central to mediating the cellular response to hypoxia. Whether hypoxia gradients regulate megakaryocyte (MK) differentiation and maturation and the possible mechanisms of these actions remain unknown. Our previous data showed that impaired proplatelet formation (PPF) contributed to the development of thrombocytopenia in ITP. Recent studies suggest that the S1P signaling pathway in MKs plays a critical role in PPF ( Blood, 2013; J EXP MED, 2012). To further explore the underlying mechanism of impaired PPF in ITP, we found that HIF-1α/SPHK2/S1P axis-mediated cytoskeletal reorganization was defective in the PPF of ITP. All-trans retinoic acid (ATRA), which has been shown to be a promising treatment option for ITP patients in our clinical studies ( Blood, 2021; Lancet Haematology, 2017; Lancet Haematology, 2021), could restore cytoskeletal reorganization and correct impaired PPF. Methods Thirty patients with newly diagnosed ITP and 30 healthy donors were included in our study. The 30 ITP patients received ATRA at a dose of 10 mg orally twice daily for 12 weeks. Bone marrow samples were taken before the first medication (Day 0) and after 12 weeks of ATRA therapy (Day 85). We employed an imaging cytometry platform to perform a comprehensive quantitative analysis of MK distribution and hypoxic status in the bone marrow microenvironment of ITP. Targeted and untargeted metabolomic profiling through metabolomic analysis was performed to explore the relationship between the metabolome and ITP. Results We analyzed the hypoxic status of MKs in the endosteal niche and perivascular niche. In healthy controls, MKs in the perivascular niche exhibited a hypoxic profile, defined by robust HIF-1α expression and strong retention of pimonidazole. MKs in the endosteal region were less hypoxic. These results reflect a spatial hypoxia gradient in the bone marrow microenvironment. In contrast, we found that, irrespective of their location, ITP MKs displayed less hypoxia with no defined spatial gradients. ITP-MKs in the perivascular niche displayed altered cytoskeletal reorganization and impaired proplatelet formation (PPF). Metabolomics data revealed a decreased S1P level in ITP patients. Downregulated sphingosine kinase 2 (SPHK2) in MKs suppressed S1P production. S1P was essential for cytoskeletal reorganization and PPF regulation. In addition, we demonstrated that hypoxia inducible factor-1α (HIF-1α) mediated SPHK2 activation and S1P production. These data suggested that a disrupted hypoxia gradient contributed to impaired PPF via the HIF-1α/SPHK2/S1P axis. We then investigated the effect of ATRA on PPF. The ITP patients received ATRA at a dose of 10 mg orally twice daily for 12 weeks. For patients who received ATRA, S1P levels, HIF-1α and SPHK2 expression levels were increased compared with the pretreatment levels. And ATRA corrected impaired PPF and restored cytoskeletal reorganization by upregulating HIF-1α. Conclusions A disrupted hypoxia gradient contributed to impaired PPF in the ITP bone marrow environment via the HIF-1α/SPHK2/S1P axis. The ATRA-induced correction of impaired PPF is a potential mechanistic explanation for the clinical efficacy of ATRA in ITP.

Decider-2: Prospective Randomized Multicenter Phase III Trial of Decitabine and Venetoclax Administered in Combination with All- Trans Retinoic Acid (ATRA) or Placebo in Patients with Acute Myeloid Leukemia Who Are Ineligible for Induction Chemotherapy

Background and Significance DNA-hypomethylating agent (HMA) based therapy is the treatment backbone for older, medically non-fit AML/MDS pts, and studies have been performed with multiple combination partners over the last years (reviewed by Stomper et al., Leukemia 2021). Recently, the combination of azacitidine or decitabine (DEC) with venetoclax (VEN) has become the novel standard for many of these pts. Based on preclinical evidence of priming of AML cells to all- trans retinoic acid (ATRA) by DEC, we have conducted a randomized phase II trial in 200 elderly and medically non-fit AML pts on the effect of ATRA as add-on to DEC (DECIDER-1, Lübbert et al., J. Clin. Oncol 2020). Median overall survival (OS) was 8.2 months with ATRA v 5.1 months without ATRA (hazard ratio, 0.65; 95% CI, 0.48 to 0.89; P = .006). Notably, ATRA did not add toxicity, the combination was active also in AML with adverse genetics, and it appeared to prolong time to secondary treatment resistance. A randomized open-label phase II trial (DEC -/+ ATRA) is also being conducted in higher-risk MDS pts (Zhou et al., ASH 2021, 539). Investigating a triple combination of HMA+VEN+ATRA is a logical next step. We could demonstrate cooperativity between these 3 drugs in AML cell lines irrespective of TP53 mutation status on cell growth inhibition and apoptosis (Bresser et al., ASH 2022, 11537). Study Design and Methods This academic study is a randomized, prospective, double-blind, placebo-controlled, parallel group, multicenter trial. It is planned to randomize 256 pts in a ratio of 1:1 to the treatment arms at ~35 sites in Germany. The primary objective is to compare the efficacy of ATRA v placebo as add-on to the standard treatment DEC+VEN with respect to OS. Secondary objectives are to compare ATRA v placebo as add-on to DAC+VEN with respect to objective best response (i.e. CR/CRi/MLFS/PR), CR with negative measurable residual disease (MRD), probability of survival with objective best response, health-related quality of life and safety. Sample size calculation is based on the primary endpoint OS. The study should have a power of 80% to demonstrate superiority of ATRA vs. placebo with respect to OS at one-sided level alpha of 2.5% under the assumption of a hazard ratio of 0.67. This requires the observation of 191 deaths. With a recruitment period of 3 years and an additional one year follow-up period, it is necessary to include 230 pts. To account for the possibility of up to 10% of the pts with incomplete follow-up, 230/0.9 = 256 pts will be randomized in total (ratio 1:1). Interim safety analyses will be performed after the 2nd cycle of the 10th randomized pt, and after the 3rd cycle of the 50th, the 100th and the 150 th randomized pt, and monitored by an Independent Data Monitoring Committee. Key inclusion criteria are: age ≥18 years; previously untreated AML (WHO 2016); ineligibility for standard induction chemotherapy; ECOG ≤ 2; WBC <25×109/L (prior cytoreduction allowed). Key exclusion criterion is: acute promyelocytic leukemia. Treatment All pts will be treated with DAC+VEN as standard treatment and will additionally either receive ATRA or placebo (Fig. 1). Study treatment is continued until relapse/progression, hematopoietic cell transplantation, death or unacceptable toxicity (whichever occurs first). Correlative investigations include serial MRD measurement, NGS profiling and apoptosis studies. Registration EUDRACT 2020-005495-36; DRKS 00023646 (P001516). Funding Funded by the German Research Foundation (DFG, project no. 367848349/LU 429/13-1); ATRA is provided free of charge by Cheplapharm (Germany). Figure 1 Overview of the study treatment

Biomarker MSC-C5b-9-Guided Master Therapies for Resistant/Recurrent ITP: A Prospective, Randomized, Open-Label, Multicenter Trial

Introduction: Immune thrombocytopenia (ITP) is an acquired organ-specific autoimmune disorder and a common bleeding disorder that poses a considerable risk to human health. Steroids, as the first-line treatment, do not provide long-term relief. Our previous clinical trials have confirmed the efficacy and safety of all-trans retinoic acid (ATRA) in the treatment of ITP and identified that the biomarker MSC-C5b-9 may be a stratification marker for evaluating the efficacy of ATRA (Haematologica, 2019; Lancet Haematol. 2017; 2021). This research aims to develop a new treatment approach for steroid-resistant/recurrent ITP based on the marker MSC-C5b-9. Method: We conducted a prospective, randomized, open-label, multicenter trial to evaluate the efficacy and safety of ATRA combined with eltrombopag based on MSC-C5b-9 as a novel treatment for steroid-resistant/recurrent ITP. Following enrollment, all patients underwent bone marrow aspiration to assess MSC-C5b-9 levels. Subsequently, patients were randomly assigned in a 1:1 ratio to either the eltrombopag group or the eltrombopag + ATRA group. In both treatment groups, the initial dose of eltrombopag was 50 mg daily, with dose adjustments based on platelet levels. For patients assigned to the ATRA group, ATRA was given at a dose of 10 mg twice daily. Peripheral blood cell counts and adverse drug reactions were regularly monitored. The primary endpoint was the sustained response rate at 18 months after randomization, and secondary endpoints include Complete Remission, Partial Remission, Relapse rate, Early Response, Initial Response, Adverse Events, and Adverse Events graded using the National Cancer Institute Common Terminology Criteria (NCI CTCAE) v5.0 criteria. The study has been registered at clinicaltrials.gov. NCT05438875. Result: From March 2023 to July 2023, a total of 30 patients with steroid-resistant/recurrent ITP were enrolled in the study and randomized 1:1 to receive eltrombopag combined with ATRA (ATRA group, n=15, MSC-C5b-9 +6, -9) or eltrombopag alone (control group, n=15, MSC-C5b-9 +6, -9) in 5 centers, and all enrolled patients were included in the intention-to-treat (ITT) analysis. In the ATRA group, the median age was 38 years (range, 29-64), consisting of 8 male patients. In the control group, the median age was 44 years (range, 23-75), consisting of 9 male patients. There were no statistically significant differences observed in the baseline clinical characteristics between the two groups. There was no difference in the bleeding score and ECOG score between the two groups (P=0.717; P=1.000). The median platelet count was comparable between the ATRA group and the control group (17 (1-28) vs. 16 (2-26), P=0.850). Comorbidities at random, such as hypertension, were comparable between the two groups (26.7% (4/15) vs. 33.3% (5/15), P=1.000). Combined autoantibody abnormalities were compared between the two groups (6.7% (1/15) vs. 6.7% (1/15), P=1.000). The rate of Early Response in the ATRA group was higher than that in the control group, but the difference was not significant (73.3% (11/15) vs. 53.5% (8/15), P=0.256). As of July 29, 2023, a total of 24 patients had been enrolled for a duration exceeding 4 weeks. Similarly, the Initial Response rate was higher in the ATRA group, but no significant difference was observed between the two groups (84.6% (11/13) vs. 63.6% (7/11), P=0.357). Nevertheless, it is noteworthy that the 4-week CR rate in the ATRA group was higher than that in the control group (76.9% (10/13) vs. 36.4% (4/11), P=0.045). What's more, the overall efficacy of the ATRA group was better than that of the control group. The mean platelet count at weeks 1, 2, 3, and 4 posttreatment, along with the mean maximum platelet count posttreatment, exhibited higher values in the ATRA group than in the control group; however, these disparities did not reach statistical significance (P=0.310; P=0.568; P=0.779; P=0.618; P=0.355). ATRA was well tolerated, and only one patient developed grade I dry mouth and headache, which improved after dose reduction. There was no difference between the ATRA and control groups in terms of medication adverse effects (13.3% (2/15) vs. 13.3% (2/15), P=1.000). Conclusions: Eltrombopag plus ATRA is an effective and well-tolerated approach for treating steroid-resistant/recurrent ITP. Eltrombopag plus ATRA can enhance patients' complete remission and is well tolerated.

All-trans retinoic acid improves NSD2-mediated RARα phase separation and efficacy of anti-CD38 CAR T-cell therapy in multiple myeloma

BackgroundImmunotherapies targeting CD38 have demonstrated salient efficacy in relapsed/refractory multiple myeloma (MM). However, loss of CD38 antigen and outgrowth of CD38 negative plasma cells have emerged as a major obstacle...

Advancement of All-Trans Retinoic Acid Delivery Systems in Dermatological Application

Dermatological conditions, such as acne, photoaging, psoriasis, and wounds, have been treated topically with all-trans retinoic acid (ATRA) for many years owing to its anti-inflammatory activity, comedolytic effect, and ability to increase collagen production. However, common side effects of ATRA known as the retinoid reaction can occur. These side effects are countered by ATRA encapsulation in solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLCs), and liposomes. Liposomes used to encapsulate ATRA include niosomes, ethosomes, and transfersomes. Side effects involving inflammatory reactions, such as irritation, redness, and erythema, were diminished using these approaches. The use of such carriers enhanced the efficacy of ATRA by enhancing its permeation into skin. These formulations have been compared in terms of improving the activity of ATRA and the ability to relieve the side effects. Further research into different delivery systems for ATRA using various formulations will improve the future of topical ATRA delivery.

S290: ATRA CAN CORRECT DEFECTIVE HIF-1Α/S1P AXIS-MEDIATED CYTOSKELETAL REORGANIZATION IN PROPLATELET FORMATION OF ITP

Background: Bone marrow physiological hypoxia plays a crucial role in haematopoietic stem cell homeostasis. Hypoxia inducible factor (HIF) is central to mediating the cellular response to hypoxia. HIF-1α expression was decreased in the bone marrow of patients with immune thrombocytopenia (ITP), and HIF-1α activation was shown to enhance megakaryopoiesis in mice. Recent studies suggest that “inside-out” signalling by S1P in megakaryocytes (MKs) plays a critical role in proplatelet formation (PPF) (Blood, 2013; J EXP MED, 2012). Our previous data indicated that impaired PPF contributed to the development of thrombocytopenia in ITP. To further explore the underlying mechanism of impaired PPF in ITP, we found that HIF-1α/S1P axis-mediated cytoskeletal reorganization was defective in the PPF of ITP. All-trans retinoic acid (ATRA), which has been shown to be a promising treatment option for ITP patients in our clinical studies (Blood, 2021; Lancet haematology, 2017; Lancet haematology, 2021), could restore cytoskeletal reorganization and correct impaired PPF. Aims: This study aimed to explore the role of hypoxia inducible factor-1α (HIF-1α) in proplatelet formation (PPF) and the underlying mechanisms of ATRA treatment in ITP patients. Methods: Thirty consecutive patients with newly diagnosed ITP and 30 healthy donors were included in our study. MKs were isolated from bone marrow samples. Targeted and untargeted metabolomic profiling through metabolomic analysis was performed to explore the relationship between the metabolome and ITP. Confocal microscopy and transmission electron microscopy were used to observe the PPF and cytoskeleton structure of ITP MKs. An ITP mouse model was established to observe the therapeutic effects of ATRA in the PPF. Results: In the present study, we observed that MKs displayed altered cytoskeletal reorganization and impaired proplatelet formation (PPF) in ITP patients. Targeted and untargeted metabolite profiling revealed a decreased sphingosine-1-phosphate (S1P) level in ITP. Downregulated sphingosine kinase 2 (SPHK2) expression in MKs accounted for the low level of S1P in ITP. S1P is essential for S1P receptor 1 (S1PR1) and Rac1 activation, Src family kinases (SFKs) activity, and subsequent cytoskeletal reorganization and PPF regulation. Moreover, we demonstrated that HIF-1α mediated SPHK2 activation and S1P production. Decreased HIF-1α levels were found in the MKs of patients with ITP, contributing to impaired PPF. We then investigated the effect of ATRA on PPF in ITP patients. ATRA upregulated HIF-1α and SPHK2 expression, increased S1P production and corrected impaired PPF in vitro. In an ITP mouse model, ATRA alleviated thrombocytopenia and restored cytoskeletal reorganization. ATRA corrected impaired PPF by upregulating HIF-1α expression. The exposure of ITP MKs to selective RARα (AM580) or RARγ (BMS961) agonists did not change PPF. However, the treatment of ITP MKs with a selective RARβ agonist (CD2314) significantly increased PPF. Furthermore, we found that the effect of ATRA on enhancing PPF in ITP MKs was reversed in the presence of an RARβ antagonist (CD2665). These data suggest that impaired PPF in ITP MKs is corrected by ATRA in a RARβ-dependent manner. Summary/Conclusion: Together, our data show that the HIF-1α/S1P axis mediates altered cytoskeletal reorganization and impaired PPF in ITP and suggest that ATRA correction of impaired PPF is a potential mechanistic explanation for the clinical efficacy of ATRA in ITP.

All-Trans Retinoic Acid Plus Low-Dose Rituximab Vs Low-Dose Rituximab in Corticosteroid-Resistant or Relapsed ITP

IntroductionApproximately one-third of immune thrombocytopenia (ITP) patients fail to achieve a response with first-line treatments, and most patients who respond to first-line treatment relapse and require further second-line therapies. Rituximab (RTX) has been frequently used in ITP treatment, and proposed schedules include the standard dose (SD) and low dose (LD). Previous studies on LD-RTX in ITP revealed a comparable overall response (OR) and reduced incidences of short- and long-term complications (e.g., infections) compared with SD-RTX (Blood, 2012; Platelets, 2019). However, LD-RTX does not achieve a rapid and long-lasting response in the treatment of ITP. Our preliminary studies demonstrated the efficacy of all-trans retinoic acid (ATRA) in the ITP model due to its effects on inducing megakaryocyte maturation and its immunomodulatory effects (Stem Cells Dev, 2017; J Thromb Haemost, 2017; Br J Haematol, 2018; Haematologica, 2019). Since RTX and ATRA share disparate mechanisms in treating ITP, a combination of RTX and ATRA may work synergistically based on a “double-hit” mechanism targeting both platelet production and destruction, which may overcome the long TTR and improve the SR rate of LD-RTX. Therefore, our study aimed to determine the efficacy and safety of ATRA plus LD-RTX compared to LD-RTX monotherapy in patients with corticosteroid-resistant or relapsed ITP (NCT03304288).MethodsEligible corticosteroid-resistant or relapsed ITP patients with a platelet count < 30 × 10 9/L or bleeding symptoms at enrolment were randomly allocated in a 2:1 ratio to receive 100 mg of RTX weekly for 6 weeks plus ATRA orally at 20 mg/m 2 daily for 12 weeks or 100 mg of RTX weekly for 6 weeks. Stable doses of concomitant corticosteroids, danazol, and cyclosporin were permitted. Treatment was discontinued if platelet counts in two consecutive tests at least 2 weeks apart were more than 300 × 10 9/L and resumed when the platelet count fell to less than 150 × 10 9/L. Assessments were performed at baseline, weekly during the first 4 weeks, every 2 weeks until week 24, and every 4 weeks thereafter. The primary outcome was OR, defined as a platelet count ≥ 30 × 10 9/L, a doubling of the baseline platelet count and the absence of bleeding. Secondary endpoints included sustained response (SR), initial response, complete response, time to response, duration of response and adverse events. SR was defined as maintenance of a platelet count > 30 × 10 9/L, the absence of bleeding, and no requirement for other ITP-specific treatment for 6 consecutive months.ResultsOne hundred sixty-eight patients from 7 tertiary medical centres in China were included between 2017 and 2020, 112 patients received combination treatment of LD-RTX and ATRA, and 56 patients received LD-RTX monotherapy. All the baseline characteristics were comparable between the two groups. The median ages of patients in the LD-RTX plus ATRA group and LD-RTX monotherapy group were 46.0 years and 44.5 years, respectively. For patients in the combination and monotherapy groups, the median number of previous therapies was 2.0. The median baseline platelet count was 17.0 × 10 9/L in the combination group and 19.0 × 10 9/L in the monotherapy group. All the patients were followed up for more than 11 months. OR was observed in 90 (80.4%) patients in the combination group and 33 (58.9%) in the LD-RTX monotherapy group (between-group difference, 0.22; 95% CI, 0.07 to 0.36), indicating that the combination treatment increased the response rate. SR was achieved by 68 (60.7%) patients in the combination group and 23 (41.1%) patients in the monotherapy group at the 6-month follow-up (between-group difference, 0.20; 95% CI, 0.04 to 0.35). Additionally, 56 (50%) subjects in the combination group and 19 (34%) in the monotherapy group were still in sustained remission at 12 months (between-group difference: 0.16; 95% CI, -0.01 to 0.33). No significant difference was found between the 2 treatment groups in terms of the time to a response. The severity of AEs was primarily of grade 1-2. The 2 most common AEs for the combination group were dry skin and headache or dizziness, with incidences of 40.2% (45/112) and 18.8% (21/112), respectively.ConclusionsIn conclusion, ATRA plus LD-RTX significantly increased the overall and sustained response, indicating a novel promising treatment option for corticosteroid-resistant or relapsed adult ITP patients. DisclosuresNo relevant conflicts of interest to declare.

Combinatorial Use of Bexarotene Plus ATRA for the Treatment of Acute Myeloid Leukemia

Aim: All-trans retinoic acid (ATRA) results in high response rates in acute promyelocytic leukemia (APL), but has not had a significant impact on non-APL forms of acute myeloid leukemia (AML), even though retinoic acid receptors have been implicated in hematopoietic maturation and self-renewal. RXRs bind as heterodimers with RARs, and are expressed at higher levels in AML cells than are RARs. We sought to determine whether natural RXR ligands exist in primary leukemia cells, whether RXR ligands might augment or inhibit leukemic cell growth, and whether RXRs might be rational targets for AML therapeutics.Background: Retinoid receptors are nuclear hormone receptors, induced during terminal myeloid maturation with highest expressed in M4 and M5 AML. Retinoids serve as intracellular messengers and are activating ligands for the retinoic acid receptors (RAR) and retinoid X receptors (RXR).Methods: We developed an in vivo reporter assay that measures intracellular, activating nuclear receptor ligands in mouse bone marrow cells. We generated transgenic mice with GFP regulated by a UAS promoter. The yeast Gal4 transcription factor recognizes UAS promoter sequences. When a fusion of the Gal4-DNA binding domain (DBD) and a retinoid receptor ligand-binding domain (LBD) is expressed in UAS-GFP bone marrow cells, and an activating ligand is present, the cells express GFP. Leukemia was generated in bone marrow cells from these mice and from Mx1-Cre x Rxrαfl/fl x Rxrβfl/fl mice using MSCV-MLL-AF9 retrovirus.Results: We found that intermediate levels of RXRA ligands are present in mouse MLL-AF9 leukemia cells in vivo. To determine if activation of RXRA is required for MLL-AF9 cell growth, we transduced MSCV-MLL-AF9 retrovirus into bone marrow cells from Mx1-Cre+ x Rxrαfl/fl x Rxrβfl/fl mice and transplanted these into recipient mice. Mx1-Cre is “leaky.” Without external activation of Mx1-Cre (i.e. without pIpC treatment) we found that all subsequent leukemias were associated with deleted (“floxed out”) Rxra and Rxrb alleles, suggesting that the deleted allele was positively selected for. In secondary transplants, we found that MLL-AF9 leukemias with deleted Rxrα and Rxrβ were associated with shorter survival when compared with MLL-AF9 leukemias with wild type Rxrα and Rxrβ, suggesting that naturally occurring RXR ligands suppressed leukemic growth. To determine if pharmacologic activation of retinoid receptors could inhibit MLL-AF9 cell growth, we treated MLL-AF9 cells ex vivo with ATRA and bexarotene. We found that ATRA modestly inhibited growth, and this effect reached a plateau at 62 nM (this may partially explain the limited clinical efficacy of ATRA in non-APL AML) (see Figure). In contrast, the EC50 of bexarotene was 125 nM and the EC50 decreased to 54 nM when bexarotene was combined with 62 nM ATRA. Higher doses of ATRA decreased the bexarotene EC50 further to 43 nM and resulted in near complete culture collapse. Finally, to determine whether combination bexarotene and ATRA inhibited cell growth by inducing differentiation or apoptosis, we examined cytomorphology, cell division by Celltrace Violet staining (similar to CFSE), and Annexin V. Unexpectedly, we observed no evidence of differentiation, but rather increased Annexin V associated with ATRA and bexarotene-induced growth arrest.Conclusion: RXRs act as tumor suppressors in MLL-AF9 murine leukemia cells in vivo, and the activation of RXR/RAR heterodimers with bexarotene and all-trans retinoic acid leads to synergistic apoptosis and growth arrest. Additional experiments are now being performed to test the efficacy of this dug combination in vivo and assess their potential use in elderly relapsed/refractory AML. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Sphingosine kinases are involved in the regulation of all-trans retinoic acid sensitivity of K562 chronic myeloid leukemia cells.

The efficacy of all-trans retinoic acid (ATRA) for the treatment of chronic myeloid leukemia (CML) has been reported to be limited both as single-drug treatment or in combination with other drugs. Our previous study demonstrated that sphingosine 1-phosphate attenuated the effects of ATRA on human colon cancer cells by blocking the expression of retinoic acid receptor β. The aim of the present study was to investigate whether the ATRA-dependent proliferation inhibition of K562 cells was regulated by sphingosine kinases (SphKs). The results of cell proliferation assay and reverse transcription-PCR demonstrated that ATRA may exert synergistic effects with the SphK1 inhibitor SKI 5C or the pan-SphK inhibitor SKI II to inhibit the proliferation of K562 cells and upregulate the expression levels of the ATRA-inducible enzyme cytochrome P450 26A1 (CYP26A1). Knocking down the expression of SphK1 or SphK2 in K562 cells by small interfering RNA enhanced the inhibitory effects of ATRA and induced the expression of CYP26A1. Crude asterosaponins, which abrogated the expression of SphK2, also enhanced the effects of ATRA on K562 cells. In conclusion, the results of the present study demonstrated that SphKs may be involved in the regulation of the sensitivity of CML cells to ATRA.

Lycopene Protects against Smoking-Induced Lung Cancer by Inducing Base Excision Repair.

Background: Oxidative stress plays a critical role in lung cancer progression. Carotenoids are efficient antioxidants. The objective of this study was to explore the efficacy of all-trans retinoic acid (ATRA) and carotenoids in cigarette smoke-induced oxidative stress within A549 human lung cancer epithelial cells. Methods: A549 cells were pretreated with 1-nM, 10-nM, 100-nM, 1-μM and 10-μM ATRA, β-carotene (BC) and lycopene for 24 h, followed by exposure to cigarette smoke using a smoking chamber. Results: The OxyBlot analysis showed that smoking significantly increased oxidative stress, which was inhibited by lycopene at 1 nM and 10 nM (p < 0.05). In the cells exposed to smoke, lycopene increased 8-oxoguanine DNA glycosylase (OGG1) expression at 1 nM, 10 nM, 100 nM, and 1 μM (p < 0.05), but not at 10 μM. Lycopene at lower doses also improved Nei like DNA glycosylases (NEIL1, NEIL2, NEIL3), and connexin-43 (Cx43) protein levels (p < 0.05). Interestingly, lycopene at lower concentrations promoted OGG1 expression within the cells exposed to smoke to an even greater extent than the cells not exposed to smoke (p < 0.01). This may be attributed to the increased SR-B1 mRNA levels with cigarette smoke exposure (p < 0.05). Conclusions: Lycopene treatment at a lower dosage could inhibit smoke-induced oxidative stress and promote genome stability. These novel findings will shed light on the molecular mechanism of lycopene action against lung cancer.

All-trans Retinoic Acid Counteracts Diarrhea and Inhibition of Downregulated in Adenoma Expression in Gut Inflammation.

Intestinal epithelial apical membrane Cl-/HCO3- exchanger DRA (downregulated in adenoma, SLC26A3) has emerged as an important therapeutic target for diarrhea, emphasizing the potential therapeutic role of agents that upregulate DRA. All-trans retinoic acid (ATRA), a key vitamin A metabolite, was earlier shown by us to stimulate DRA expression in intestinal epithelial cells. However, its role in modulating DRA in gut inflammation has not been investigated. Our aim was to analyze the efficacy of ATRA in counteracting inflammation-induced decrease in DRA in vitro and in vivo. Interferon-γ (IFN-γ)-treated Caco-2 cells and dextran sulfate sodium (DSS)-treated C57BL/6J mice served as in vitro and in vivo models of gut inflammation, respectively. The effect of ATRA on IFN-γ-mediated inhibition of DRA function, expression, and promoter activity were elucidated. In the DSS colitis model, diarrheal phenotype, cytokine response, in vivo imaging, myeloperoxidase activity, and DRA expression were measured in the distal colon. All-trans retinoic acid (10 μM, 24 h) abrogated IFN-γ (30 ng/mL, 24 h)-induced decrease in DRA function, expression, and promoter activity in Caco-2 cells. All-trans retinoic acid altered IFN-γ signaling via blocking IFN-γ-induced tyrosine phosphorylation of STAT-1. All-trans retinoic acid cotreatment (1 mg/kg BW, i.p. daily) of DSS-treated mice (3% in drinking water for 7 days) alleviated colitis-associated weight loss, diarrheal phenotype, and induction of IL-1β and CXCL1 and a decrease in DRA mRNA and protein levels in the colon. Our data showing upregulation of DRA under normal and inflammatory conditions by ATRA demonstrate a novel role of this micronutrient in alleviating IBD-associated diarrhea.

Lipid-polymer nanoparticles with CD133 aptamers for targeted delivery of all-trans retinoic acid to osteosarcoma initiating cells

Osteosarcoma, a common type of bone cancer in children, and represents an aggressive and fetal cancer worldwide. Osteosarcoma initiating cells are considered to be a subpopulation of cancer cells which contribute to the progression, recurrence, metastasis and multi-drug resistance of osteosarcoma. CD133 is considered to be one marker for osteosarcoma initiating cells. All-trans retinoic acid (ATRA), an active metabolite of vitamin A under the family retinoid, is an up-and-coming drug which was able to effectively treat various cancer initiating cells. Nevertheless, there have been no research that reported the activity of ATRA against osteosarcoma initiating cells. In this research, we hereby examined the potential activity of ATRA in osteosarcoma initiating cells, and developed lipid-polymer nanoparticles with CD133 aptamers for targeted ATRA delivery to osteosarcoma initiating cells. Using the cytotoxicity assay, colony formation assay, tumorsphere formation assay and flow cytometry, the therapeutic effect of ATRA and ATRA-loaded lipid-polymer nanoparticles conjugated with CD133 aptamers (ATRA-PLNP-CD133) against osteosarcoma initiating cells were investigated. The results showed that ATRA exerted potent activity towards osteosarcoma initiating cells. ATRA-PLNP-CD133, which showed a size of 129.9 nm and a sustained release of ATRA during 144 h, was demonstrated to efficiently and specifically promote the ATRA delivery to osteosarcoma initiating cells, and achieve superior therapeutic efficacy in osteosarcoma compared with ATRA and non-targeted nanoparticles. This is the first report of the therapeutic efficacy of ATRA towards osteosarcoma initiating cells, and the increased ATRA delivery by nanoparticles to osteosarcoma initiating cells using CD133 aptamers. ATRA-PLNP-CD133 represent an up-and coming approach for the therapy of osteosarcoma initiating cells.

Anti-Fibrotic Potential of All Trans Retinoic Acid in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) embraces Crohn’s disease (CD), ulcerative colitis (UC) and the less common indeterminate colitis, all chronic inflammatory processes of the gastrointestinal (GI) tract. Together, they cause significant morbidity for a million and a half Americans [1]. Symptoms include diarrhea, nausea, abdominal pain, weight loss, which can occasionally prove fatal (i.e., toxic megacolon, perforated bowel) [2]. Patients are also at increased risk for colorectal cancer [3]. First line treatments, including various anti-inflammatory agents and antibiotics, are variably effective against active disease [4]. Remissions can be short-lived and uncontrolled activity is associated with significant side-effects [3]. Gut fibrosis will require most patients (80% and 45% of CD and UC patients, respectively) to undergo surgery [4]. Over the last decade, the so-called biological response modifiers or ‘biologics’, macromolecules that target inflammatory lymphocytes or the cytokines they produce, have emerged as effective therapeutic agents [5]. For example, infliximab, a chimeric anti-human tumor necrosis factor (TNF)-α antibody earned FDA approval almost 20 years ago, based on a high response rate, significant mucosal and fistula healing and long-term remissions in both CD and UC. Additional targets of biologics, either marketed or in various stages of development, include anti-p40, anti-p19, anti-interleukin (IL)-12/23, and anti-alpha 4/beta 7 integrin antibodies [5, 6]. However, an estimated 30% of patients will not respond to such treatments, and of those who initially respond, 50% will relapse within a year risking significant, often serious side effects including infections and increased risk of cancer. So far, biologics have had only a modest impact on surgery rates [7]. The need for novel therapies remains acute. Literature reports indicate that All trans retinoic acid (ATRA) provides benefit in various rodent models of IBD, including potential anti-fibrotic activity [8, 9]. Retinoic acid can exist in the body as any of five different chemical isomers (all-trans-RA, 9-cisRA, 13-cisRA, 11-cisRA and 9, 13-dicisRA). ATRA is the biologically active isomer and the primary enzymatic product of retinaldehyde oxidation. The retinoic acid family regulates a wide range of biological processes, including embryonic development, reproduction, vision, cell growth and differentiation, as well as, apoptosis and inflammation [10]. Topical ATRA is known as tretinoin, and is currently marketed under several trade names such as Retin-A®, Retin-A Micro®, Atralin®, Renova®, and Avita® as FDA approved topical treatment for acne and skin wrinkles. Oral formulations, called isotretinoin (Accutane®, Claravis®, Sotret® and Amnesteem® and Vesanoid®) can cure severe acne and treat acute promyelocytic leukemia (APL), but oral dosing induces more severe side effects. Isotretinoin has not been tested in IBD clinical trials, perhaps due to the serious side effects associated with oral administration, including teratogenicity, suicidality, headache, dizziness, fever, weakness, tiredness, dry mouth, dry skin, other skin changes, thinning hair, nausea, vomiting, itching, bone pain, mouth sores, increased sweating, earaches, and perhaps even colitis. Black-box warnings for oral formulations have been issued by the FDA because of these serious side effects, including retinoic acid syndrome in APL patients. Retinoic acid syndrome may manifest as life threatening upper respiratory tract disturbances (dyspnea, respiratory insufficiency, pleural effusion, expiratory wheezing and increased susceptibility to pneumonia). Its frequency, mechanism and treatment have recently been reviewed [11]. Efforts to circumvent toxicities by tissue targeted administration have included encapsulation in liposomes and aerosolization, although none of these have progressed further in development or resulted in marketed products [12,13]. This review begins with an analysis of published studies bearing on the efficacy of ATRA as an anti-inflammatory treatment for IBD, including in vitro and in vivo work in rodents, as well as ex vivo studies using human tissues. Clinical reports about ATRA attenuation or induction of IBD will also be reviewed. Efforts to deliver ATRA directly to gut tissue to improve activity and reduce side effects will then be discussed. Finally, the potential of ATRA to treat fibrosis will be considered. If successful, oral delivery of ATRA directly to the immune structures of the gut could represent a novel IBD therapy with a potential to reduce fibrosis and the subsequent need for surgery.

All trans retinoic acid modulates TNF-α and CYP2E1 pathways and enhances regression of ethanol-induced fibrosis markers in hepatocytes and HSCs in abstaining rodent model

Context: Our previous studies showed that all trans retinoic acid (ATRA) ameliorates alcohol-induced toxicity. Hence, we evaluated the efficacy of ATRA and abstention in the regression of alcohol-induced hepatotoxicity.Materials and methods: After ethanol administration to rats for 90 days, the regression of alcohol-induced toxicity was studied by supplementing ATRA at a dose of 100 μg/kg body weight for 30 days. It was also compared with animals in abstention.Results and discussion: Ethanol administration enhanced oxidative stress, activated HSCs and increased collagen deposition. All these alterations were reversed to a certain extent by ATRA supplementation.Conclusions: ATRA had better efficacy than just abstention in reducing ethanol-induced toxicity. The mechanism might be downregulation of CYP2E1, leading to reduced oxidative stress in the hepatocytes and thus impeding NFκB activation, cytokine production, activation of HSC and resulting in the reduction of inflammation and remodelling of fibrosis by modulating MMP and TIMP.

A novel controlled release formulation of the Pin1 inhibitor ATRA to improve liver cancer therapy by simultaneously blocking multiple cancer pathways

Hepatocellular carcinoma (HCC) is the second leading cause of cancer deaths worldwide largely due to lack of effective targeted drugs to simultaneously block multiple cancer-driving pathways. The identification of all-trans retinoic acid (ATRA) as a potent Pin1 inhibitor provides a promising candidate for HCC targeted therapy because Pin1 is overexpressed in most HCC and activates numerous cancer-driving pathways. However, the efficacy of ATRA against solid tumors is limited due to its short half-life of 45min in humans. A slow-releasing ATRA formulation inhibits solid tumors such as HCC, but can be used only in animals. Here, we developed a one-step, cost-effective route to produce a novel biocompatible, biodegradable, and non-toxic controlled release formulation of ATRA for effective HCC therapy. We used supercritical carbon dioxide process to encapsulate ATRA in largely uniform poly L-lactic acid (PLLA) microparticles, with the efficiency of 91.4% and yield of 68.3%, and ~4-fold higher Cmax and AUC over the slow-releasing ATRA formulation. ATRA-PLLA microparticles had good biocompatibility, and significantly enhanced the inhibitory potency of ATRA on HCC cell growth, improving IC50 by over 3-fold. ATRA-PLLA microparticles exerted its efficacy likely through degrading Pin1 and inhibiting multiple Pin1-regulated cancer pathways and cell cycle progression. Indeed, Pin1 knock-down abolished ATRA inhibitory effects on HCC cells and ATRA-PLLA did not inhibit normal liver cells, as expected because ATRA selectively inhibits active Pin1 in cancer cells. Moreover ATRA-PLLA microparticles significantly enhanced the efficacy of ATRA against HCC tumor growth in mice through reducing Pin1, with a better potency than the slow-releasing ATRA formulation, consistent with its improved pharmacokinetic profiles. This study illustrates an effective platform to produce controlled release formulation of anti-cancer drugs, and ATRA-PLLA microparticles might be a promising targeted drug for HCC therapy as PLLA is biocompatible, biodegradable and nontoxic to humans.

All-Trans Retinoic Acid plus Arsenic Trioxide versus All-Trans Retinoic Acid plus Chemotherapy for Newly Diagnosed Acute Promyelocytic Leukemia: A Meta-Analysis.

BackgroundRecently, the all-trans retinoic acid (ATRA) plus arsenic trioxide (ATO) protocol has become a promising first-line therapeutic approach in patients with newly diagnosed acute promyelocytic leukemia (APL), but its benefits compared with standard ATRA plus chemotherapy regimen needs to be proven. Herein, we conducted a meta-analysis comparing the efficacy of ATRA plus ATO with ATRA plus chemotherapy for adult patients with newly diagnosed APL.MethodsWe systematically searched biomedical electronic databases and conference proceedings through February 2016. Two reviewers independently assessed all studies for relevance and validity.ResultsOverall, three studies were eligible for inclusion in this meta-analysis, which included a total of 585 patients, with 317 in ATRA plus ATO group and 268 in ATRA plus chemotherapy group. Compared with patients who received ATRA and chemotherapy, patients who received ATRA plus ATO had a significantly better event-free survival (hazard ratio [HR] = 0.38, 95% confidence interval [CI]: 0.22–0.67, p = 0.009), overall survival (HR = 0.44, 95% CI: 0.24–0.82, p = 0.009), complete remission rate (relative risk [RR] = 1.05; 95% CI: 1.01–1.10; p = 0.03). There were no significant differences in early mortality (RR = 0.48; 95% CI: 0.22–1.05; p = 0.07).ConclusionThus, this analysis indicated that ATRA plus ATO protocol may be preferred to standard ATRA plus chemotherapy protocol, particularly in low-to-intermediate risk APL patients. Further larger trials were needed to provide more evidence in high-risk APL patients.

Fungistatic activity of all-trans retinoic acid against Aspergillus fumigatus and Candida albicans.

PurposeFungal infections are a major complication in hematologic and neoplastic patients causing severe morbidity and mortality. Aspergillus fumigatus and Candida albicans are among the most invasive opportunistic pathogens in immunocompromised patients, and classic antifungal drugs are frequently unsuccessful in these patients. Recent reports hypothesize that the antifungal efficacy of all-trans retinoic acid (ATRA) is mainly related to its strong capacity to stimulate monocyte-mediated immunity, but no consideration was given to its potential direct fungistatic activity. Moreover, ATRA offers the opportunity for systemic therapy.Methods and resultsWe investigated the efficacy of ATRA at different concentrations for its antifungal activity against opportunistic A. fumigatus and C. albicans obtained from clinical samples according to standard protocols. A fungistatic activity of ATRA on A. fumigatus and C. albicans at 0.5–1 mM concentration was documented up to 7 days.ConclusionThis is the first evidence of a direct and strong fungistatic activity of ATRA against A. fumigatus and C. albicans. The potential adjuvant therapeutic application of ATRA might be useful in the treatment and/or prevention of systemic mycoses in immunocompromised patients. The discovery of a direct fungistatic activity, in association with its reported immunomodulatory properties, makes ATRA an excellent candidate for new combined antifungal strategies for systemic mycoses in immunocompromised and cancer patients.

Restoration of CCAAT Enhancer Binding Protein Alpha P42 Overcomes Myeloid Differentiation Block and All-Trans Retinoic Acid Resistance in Human Acute Promyelocytic Leukemia NB4-R1 Cells

All-trans retinoic acid (ATRA) is one of the first line agents in differentiation therapy for acute promyelocytic leukemia (APL). However, drug resistance becomes a major problem which influences the efficacy of ATRA. Mechanisms of ATRA resistance are ugly needed to be identified. Here we found that expression of C/EBPα, an important transcription factor for myeloid differentiation, was significantly suppressed in ATRA resistant APL cell line NB4-R1 compared with ATRA sensitive NB4 cells. Moreover, two forms of C/EBPα were unequally suppressed in NB4-R1 cells. Suppression of the full-length form P42 was more pronounced than the truncated form P30. Inhibition of PI3K/Akt/mTOR pathway was also observed in NB4-R1 cells. Meanwhile, C/EBPα expression was reduced by PI3K inhibitor LY294002 and mTOR inhibitor RAD001 in NB4 cell, suggesting that inactivation of the PI3K/Akt/mTOR pathway was responsible for C/EBPα suppression in APL cells. Then, we restored C/EBPα P42 and P30 by lentivirus vectors in NB4-R1 cells respectively, and found C/EBPα P42, but not P30, could increase CD11b, CD14, G-CSFR and GM-CSFR expression, which indicated the occurrence myeloid differentiation. Moreover, further upregulating of CD11b expression and differential morphological changes were found in NB4-R1 cells with restored C/EBPα P42 after ATRA treatment. However, CD11b expression and differential morphological changes could not be induced by ATRA in NB4-R1 cells infected with P30 expressing or control vector. Thus, we inferred that ATRA sensibility of NB4-R1 cells was enhanced by restoration of C/EBPα P42. In addition, we used histone deacetylase inhibitor trichostatin (TSA) to restore C/EBPα expression in NB4-R1 cells. Similar enhancement of myeloid differentiation and cell growth arrest were detected. Together, this study demonstrated that suppression of C/EBPα P42 induced by PI3K/Akt/mTOR inhibition impaired the differentiation and ATRA sensibility of APL cells. Restoring C/EBPα P42 is an attractive approach for differentiation therapy in ATRA resistant APL. DisclosuresNo relevant conflicts of interest to declare.

Inhibition of the PI3K/AKT/mTOR Pathway Leads to Down-Regulation of c-Myc and Overcomes Resistance to ATRA in Acute Myeloid Leukemia

Acute Promyelocytic Leukemia (APL) accounts for 5% of all cases of acute myeloid leukemia (AML). This disease is highly curable with all-trans-retinoic acid (ATRA) based therapy. In non-APL AML, ATRA has limited activity, and little is known about mechanisms of ATRA resistance. The apparent selective efficacy of ATRA in PML/RARα-associated APL poses an important question as to whether the presence of this fusion protein renders APL uniquely susceptible. Two compelling arguments can be made to counter this view. First, experiments in vitro show that ATRA effectively differentiates HL-60 cell lines, which lack the PML/RARα fusion protein. Second, clinical studies with ATRA in previously untreated older AML patients (excluding APL) have reported clinical activity. These observations confirm the therapeutic potential of ATRA beyond APL. In this context, our group has previously identified the lysine demethylase LSD-1, as a therapeutic target to re-sensitize leukemic blasts to ATRA. A clinical investigation of ATRA combined with LSD-1 inhibition is currently underway (NCT02273102). It is likely that other defects leading to ATRA resistance will be similarly amenable to pharmacologic manipulation. Defects in the proto-oncogene c-Myc have been widely implicated in the initiation and maintenance of AML. Over-expression of c-Myc in leukemic blasts enhances clonogenic survival and blocks ATRA induced differentiation. We hypothesized that down-regulation of c-Myc might increase the anti-leukemic effects of ATRA in AML. To date, c-Myc has been an evasive target for direct pharmacologic inhibition however, inhibitors of the PI3K/AKT/mTOR pathway have been shown to indirectly lower levels of c-Myc in leukemic blasts.In the current study, we show that the pro-differentiation effects of ATRA are markedly potentiated when combined with agents that target PI3K/AKT/mTOR signalling. In AML cell lines and primary patient samples, we observed additive pro-differentiation effects when ATRA was combined with inhibitors of PI3K (ZSTK474) and mTOR complex proteins (Torin-1, WYE-125132). However, when combined with the bromodomain inhibitor NVP-BEZ235, a dual inhibitor of PI3K and mTOR, we observed synergistic induction of CD11b by FACS analysis. Combination studies revealed loss of cell viability, cell cycle arrest in G1 phase, and impaired clonogenic survival, which was more prominent for ATRA combination treatments than with any agent used alone (Figure 1). To assess the role of c-Myc in mediating these effects, we measured c-Myc protein levels and PI3K/AKt/mTOR pathway markers at different time-points following treatment with ATRA alone and in combination with the inhibitors described above (Figure 2). Our findings suggest that ATRA alone quickly down-regulates c-Myc (within 6 hours) through transcriptional repression. Disruption of the PI3K/AKT/mTOR pathway further down-regulates c-Myc (within 3 hours) through destabilization and enhanced degradation. ATRA combined with NVP-BEZ235 produced maximal c-Myc suppression, and led to more cell kill than any other combination tested. Detailed analysis of changes in the transcriptome in MV-411 cells following treatment with ATRA and NVP-BEZ235 revealed that both agents act jointly on the regulation of the same biological pathways and processes, but regulate different sets of genes within these pathways. Updated mechanism based studies will be presented.In conclusion, suppression of c-Myc levels through disruption of PI3K/AKT/mTOR signalling augments the anti-leukemic effects of ATRA. These data support the clinical investigation of ATRA combined with rapalogs or bromodomain inhibitors. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Restoration of CCAAT enhancer binding protein α P42 induces myeloid differentiation and overcomes all-trans retinoic acid resistance in human acute promyelocytic leukemia NB4-R1 cells.

All-trans retinoic acid (ATRA) is one of the first line agents in differentiation therapy for acute promyelocytic leukemia (APL). However, drug resistance is a major problem influencing the efficacy of ATRA. Identification of mechanisms of ATRA resistance are urgenly needed. In the present study, we found that expression of C/EBPα, an important transcription factor for myeloid differentiation, was significantly suppressed in ATRA resistant APL cell line NB4-R1 compared with ATRA sensitive NB4 cells. Moreover, two forms of C/EBPα were unequally suppressed in NB4-R1 cells. Suppression of the full-length form P42 was more pronounced than the truncated form P30. Inhibition of PI3K/Akt/mTOR pathway was also observed in NB4-R1 cells. Moreover, C/EBPα expression was reduced by PI3K inhibitor LY294002 and mTOR inhibitor RAD001 in NB4 cells, suggesting that inactivation of the PI3K/Akt/mTOR pathway was responsible for C/EBPα suppression in APL cells. We restored C/EBPα P42 and P30 by lentivirus vectors in NB4-R1 cells, respectively, and found C/EBPα P42, but not P30, could increase CD11b, CD14, G-CSFR and GM-CSFR expression, which indicated the occurrence of myeloid differentiation. Further upregulating of CD11b expression and differential morphological changes were found in NB4-R1 cells with restored C/EBPα P42 after ATRA treatment. However, CD11b expression and differential morphological changes could not be induced by ATRA in NB4-R1 cells infected with P30 expressing or control vector. Thus, we inferred that ATRA sensitivity of NB4-R1 cells was enhanced by restoration of C/EBPα P42. In addition, we used histone deacetylase inhibitor trichostatin (TSA) to restore C/EBPα expression in NB4-R1 cells. Similar enhancement of myeloid differentiation and cell growth arrest were detected. Together, the present study demonstrated that suppression of C/EBPα P42 induced by PI3K/Akt/mTOR inhibition impaired the differentiation and ATRA sensitivity of APL cells. Restoring C/EBPα P42 is an attractive approach for differentiation therapy in ATRA resistant APL.