μM All-trans Retinoic Acid Research Articles

All-trans-retinoic acid modulates glycolysis via H19 and telomerase: the role of mir-let-7a in estrogen receptor-positive breast cancer cells

BackgroundBreast cancer (BC) is the most commonly diagnosed cancer in women. Treatment approaches that differ between estrogen-positive (ER+) and triple-negative BC cells (TNBCs) and may subsequently affect cancer biomarkers, such as H19 and telomerase, are an emanating delight in BC research. For instance, all-trans-Retinoic acid (ATRA) could represent a potent regulator of these oncogenes, regulating microRNAs, mostly let-7a microRNA (miR-let-7a), which targets the glycolysis pathway, mainly pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) enzymes. Here, we investigated the potential role of ATRA in H19, telomerase, miR-let-7a, and glycolytic enzymes modulation in ER + and TNBC cells.MethodsMCF-7 and MDA-MB-231 cells were treated with 5 µM ATRA and/or 100 nM fulvestrant. Then, ATRA-treated or control MCF-7 cells were transfected with either H19 or hTERT siRNA. Afterward, ATRA-treated or untreated MDA-MB-231 cells were transfected with estrogen receptor alpha ER(α) or beta ER(β) expression plasmids. RNA expression was evaluated by RT‒qPCR, and proteins were assessed by Western blot. PKM2 activity was measured using an NADH/LDH coupled enzymatic assay, and telomerase activity was evaluated with a quantitative telomeric repeat amplification protocol assay. Student’s t-test or one-way ANOVA was used to analyze data from replicates.ResultsOur results showed that MCF-7 cells were more responsive to ATRA than MDA-MB-231 cells. In MCF-7 cells, ATRA and/or fulvestrant decreased ER(α), H19, telomerase, PKM2, and LDHA, whereas ER(β) and miR-let-7a increased. H19 or hTERT knockdown with or without ATRA treatment showed similar results to those obtained after ATRA treatment, and a potential interconnection between H19 and hTERT was found. However, in MDA-MB-231 cells, RNA expression of the aforementioned genes was modulated after ATRA and/or fulvestrant, with no significant effect on protein and activity levels. Overexpression of ER(α) or ER(β) in MDA-MB-231 cells induced telomerase activity, PKM2 and LDHA expression, in which ATRA treatment combined with plasmid transfection decreased glycolytic enzyme expression.ConclusionsTo the best of our knowledge, our study is the first to elucidate a new potential interaction between the estrogen receptor and glycolytic enzymes in ER + BC cells through miR-let-7a.

Triphenyltin isoselenocyanate: a novel nuclear retinoid X receptor ligand with antiproliferative and cytotoxic properties in cell lines derived from human breast cancer

Several commercially available triorganotin compounds were previously found to function as agonist ligands for nuclear retinoid X receptor (RXR) molecules. Triphenyltin isoselenocyanate (TPT-NCSe), a novel selenium atom containing a derivative of triorganotin origin, was found to represent a new cognate bioactive ligand for RXRs. TPT-NCSe displayed a concentration- and time-dependent decrease in the cell viability in both human breast carcinoma MCF-7 (estrogen receptor positive) and MDA‑MB‑231 (triple negative) cell lines. Reactive oxygen species levels generated in response to TPT-NCSe were significantly higher in both carcinoma cell lines treated with TPT-NCSe when compared to mock-treated samples. Treatment with 500 nM TPT-NCSe caused a decrease in SOD1 and increased SOD2 mRNA in MCF-7 cells. The levels of SOD2 mRNA were more increased following the treatment with TPT-NCSe along with 1 μM all-trans retinoic acid (AtRA) in MCF-7 cells. An increased superoxide dismutase SOD1 and SOD2 mRNA levels were also detected in combination treatment of 500 nM TPT-NCSe and 1 μM AtRA in TPT-NCSe-treated MDA-MB-231 cells. The data have also shown that TPT-NCSe induces apoptosis via a caspase cascade triggered by the mitochondrial apoptotic pathway. TPT-NCSe modulates the expression levels of apoptosis‑related proteins, Annexin A5, Bcl‑2 and BAX family proteins, and finally, it enhances the expression levels of its cognate nuclear receptor subtypes RXRalpha and RXRbeta.

Combined dandelion extract and all-trans retinoic acid induces cytotoxicity in human breast cancer cells

Breast cancer is one of the most prevalent and deadly cancers among women worldwide. Recently, natural compounds have been widely used for the treatment of breast cancer. Present study evaluated antiproliferative and anti-metastasis activities of two natural compounds of dandelion and all-trans-retinoic acid (ATRA) in human MCF-7 and MDA-MB231 breast cancer cells. We also evaluated the expression of MMP-2, MMP-9, IL-1β, p53, NM23 and KAI1 genes. Data showed a clear additive cytotoxic effect in concentrations of 40 μM ATRA with 1.5 and 4 mg/ml of dandelion extract in MCF-7 and MDA-MB231 cells, respectively. In both cell lines, compared with the untreated cells, the expression levels of MMP-9 and IL-1β were significantly decreased while p53 and KAI1 expression levels were increased. Besides, MMP-2 and NM23 had different expressions in the two studied cell lines. In conclusion, dandelion/ATRA co-treatment, in addition to having strong cytotoxic effects, has putative effects on the expression of anti-metastatic genes in both breast cancer cells.

Excess vitamin a might contribute to submucous clefting by inhibiting WNT-mediated bone formation.

Cleft lip and/or palate (CLP) is a common craniofacial birth defect caused by genetic as well as environmental factors. The phenotypic spectrum of CLP also includes submucous clefts with a defect in the palatal bone. To elucidate the contribution of vitamin A, we evaluated the effects of the vitamin A metabolite all-trans retinoic acid (ATRA) on the osteogenic differentiation and mineralization of mouse embryonic palatal mesenchymal cells (MEPM). MEPM cells were isolated from the prefusion palates of E13 mouse embryos from three different litters. MEPM cells were cultured with and without 0.5μM ATRA in osteogenic medium. Differentiation was analysed by the expression of osteogenic marker genes and alkaline phosphatase (ALP) activity after 1, 2, and 7 days. The expression of Wnt marker genes was also analysed. Mineralization was assessed by alizarin red staining after 7, 14, 21, and 28 days. The bone marker genes Sp7, Runx2, Alpl, and Col1a1 were inhibited 10% ± 2%, 59% ± 7%, 79% ± 12% and 57% ± 20% (P < .05) at day 7. ALP activity was inhibited at days 1 and 7 by 35 ± 0% (P < .05) and 23 ± 6% (P < .001). ATRA also inhibited mineralization at 3 and 4 weeks. Finally, expression of the universal Wnt marker gene Axin2 was strongly reduced, by 31 ± 18% (P < .001), at day 7. Our data indicate that ATRA (vitamin A) inhibits bone formation by reducing Wnt signalling. This might contribute to the molecular aetiology of submucous clefting.

The effect of all‐trans retinoic acid on the mitochondrial function and survival of cardiomyoblasts exposed to local photodamage

AbstractUsing H9C2 cardiomyoblasts, we have shown that all‐trans retinoic acid (ATRA), the biologically active metabolite of vitamin A, affects mitochondrial dynamics and functions. The low dose (10 nM) ATRA stimulates the expression of nuclear retinoid receptors and induces mechanisms that are protective against severe local damage caused by laser irradiation at the mitochondrial level. These changes include increased density of the mitochondrial network, higher number of mitochondrial junctions, and enhanced mitochondrial velocity. Moreover, the treated cells had lower basal level of reactive oxygen species (ROS) and could maintain mitochondrial potential (ΔΨm) after photodamage. Cells treated with 10 nM ATRA had significantly better survival rate after photodamage in comparison to control cells. Cells treated with pharmacological concentration of ATRA (1 µM) expressed higher mitochondrial connectivity without increased motility, which did not lead to better survival or decreased ROS level as was in the case of low‐dose ATRA. The proteomics analysis showed changes in proteins related to cellular metabolism (glycolysis) and respiration in ATRA‐treated cells. The l‐lactate assay confirmed the shift to anaerobic glycolysis in cells treated with 1 µm ATRA, whereas the 10 nM ATRA decreased the level of lactate in medium. The increased levels of cytochrome c or peroxiredoxins 5 level and also lower expression of retinoid and rexinoid receptors were observed in cells treated with 1 µM ATRA. The effect of ATRA is concentration‐dependent; the increased mitochondrial dynamics and slower metabolism at 10 nM ATRA contributed significantly to the chance of survival of the cells after photodamage whereas the higher concentration of ATRA overrode the protective effect and led to the unfavorable ones.

Synthesis of 4,4-Disubstituted 3,4-Dihydropyrimidin-2(1H)-ones and -thiones, the Corresponding Products of Biginelli Reaction Using Ketone, and Their Antiproliferative Effect on HL-60 Cells.

An efficient synthetic method for novel 4,4-disubstituted 3,4-dihydropyrimidin-2(1H)-ones 5 and -thiones 6 was developed. The cyclocondensation reaction of O-methylisourea hemisulfate salt 11 with 8 gives a tautomeric mixture of dihydropyrimidines 12 and 13 following acidic hydrolysis of the cyclized products to produce 5 in high yields. Thionation reaction of 5 at the 2-position smoothly proceeds to give 2-thioxo derivatives 6. These compounds 5 and 6, corresponding to the products of a Biginelli-type reaction using urea or thiourea, a ketone and a 1,3-dicarbonyl compound, have long been inaccessible and hitherto unavailable for medicinal chemistry. These methods are invaluable for the synthesis of 5 and 6, which have been inaccessible by conventional methods. Therefore, the synthetic methods established in this study will expand the molecular diversity of their related derivatives. These compounds were also assessed for their antiproliferative effect on a human promyelocytic leukemia cell line, HL-60. Treatment of 10 µM 6b and 6d showed high inhibitory activity similarly to 1 µM all-trans retinoic acid (ATRA), indicating that the 2-thioxo group and length of two alkyl substituents at the 4-position are strongly related to activity.

Dysregulation of lipid metabolism in PLHC-1 and ZFL cells exposed to tributyltin an all-trans retinoic acid

There is increasing awareness that exposure to endocrine disrupters interferes with lipid homeostasis in vertebrates, including fish. Many of these compounds exert their action by binding to nuclear receptors, such as peroxisome proliferator-activated receptors and retinoid X receptor. This work investigates the use of fish liver cells (PLHC-1 and ZFL cells) for the screening of metabolic and lipid disrupters in the aquatic environment by assessing changes in the cell’s lipidome after exposure to the model compounds, tributyltin chloride and all-trans retinoic acid. Lipid extracts, analyzed by FIA-ESI (+/-) Orbitrap, evidenced the intracellular accumulation of triglycerides and diglycerides in both cell models after exposure to 100 and 200 nM tributyltin chloride for 24 h. Exposure to 1 μM all-trans retinoic acid led to a significant accumulation of triglycerides in PLHC-1 cells, while few triglycerides were accumulated in ZFL cells. Retinoic acid (cyp26b1, cyp3a65, lrata) and lipid metabolism (fasn, scd, elovl6) related genes were up-regulated by tributyltin chloride and all-trans retinoic acid, while only all-trans retinoic acid down-regulated the expression of dgat1a. The two cell models show sensitivity and responses to tributyltin chloride and all-trans retinoic acid comparable to those previously reported in mammalian cells. These results support the use of fish liver cells as alternative models for the detection of contaminants that act as lipid disrupters in the aquatic environment.

Molecular iodine synergized and sensitized neuroblastoma cells to the antineoplastic effect of ATRA.

Neuroblastoma (NB) is the most common solid childhood tumor, and all-trans retinoic acid (ATRA) is used as a treatment to decrease minimal residual disease. Molecular iodine (I2) induces differentiation and/or apoptosis in several neoplastic cells through activation of PPARγ nuclear receptors. Here, we analyzed whether the coadministration of I2 and ATRA increases the efficacy of NB treatment. ATRA-sensitive (SH-SY5Y), partially-sensitive (SK-N-BE(2)), and non-sensitive (SK-N-AS) NB cells were used to analyze the effect of I2 and ATRA in vitro and in xenografts (Foxn1 nu/nu mice), exploring actions on cellular viability, differentiation, and molecular responses. In the SH-SY5Y cells, 200 μM I2 caused a 100-fold (0.01 µM) reduction in the antiproliferative dose of ATRA and promoted neurite extension and neural marker expression (tyrosine hydroxylase (TH) and tyrosine kinase receptor alpha (Trk-A)). In SK-N-AS, the I2 supplement sensitized these cells to 0.1 μM ATRA, increasing the ATRA-receptor (RARα) and PPARγ expression, and decreasing the Survivin expression. The I2 supplement increased the mitochondrial membrane potential in SK-N-AS suggesting the participation of mitochondrial-mediated mechanisms involved in the sensibilization to ATRA. In vivo, oral I2 supplementation (0.025%) synergized the antitumor effect of ATRA (1.5 mg/kg BW) and prevented side effects (body weight loss and diarrhea episodes). The immunohistochemical analysis showed that I2 supplementation decreased the intratumoral vasculature (CD34). We suggest that the I2 + ATRA combination should be studied in preclinical and clinical trials to evaluate its potential adjuvant effect in addition to conventional treatments.

Cell Adhesion Expelling Analysis for Discriminating the State of Differentiation in HL60 Using Dielectrophoretic Force

We provide a novel method to discriminate the cells binding with molecules immobilized on a glass substrate by using the repulsive force of negative dielectrophoresis. The device consists of a lower substrate with interdigitated (IDA) patterns (12 μm in width and 50 μm in gap) of indium-tin oxide (ITO) and an upper ITO substrate disposed on the lower substrate. When an AC voltage is applied to a pair of microband electrodes comprising IDA to the upper ITO substrate connected to the ground, the cells are pressed onto gaps between the microband electrodes, and adhesion of the cells to the substrate is promoted (1st patterning in Fig. A). Subsequently, when an AC voltage is microband electrode “a” against the microband “b” and the upper ITO connected to the ground, the weakest region of the electric field is formed just above the microband “b”, and the cells move there by the repulsive force of negative dielectrophoresis (2nd patterning in Fig. B). At this time, if the cells adhered to the substrate via binding to molecules immobilized on the lower substrate, the cells remain on the gaps. Cells that do not interact with the molecules are expelled on the microband electrode. These procedures provide a rapid method for evaluating the expression of surface proteins that interact with molecules on the lower substrate in as little as 2 min; 60 sec in an adhesion and 60 sec in an expelling.The proposed method was applied to identify the differentiation status of HL60. Undifferentiated HL60 is known to express CD13 but not CD11b, while HL60 differentiated into neutrophils and monocytic lineages is known to up-regulate CD11b expression and down-regulate CD13 expression. In the device pretreated with anti-CD11b antibody, almost all HL60 formed well-defined linear patterns on the gaps between the microband electrodes at the 1st patterning by applying the ac voltage (100 kHz in frequency and 20 Vpp in voltage) for 60 seconds and aligned on the microband electrode “b” after 2nd patterning (day 0 in Fig. B). This result suggests that CD11b rarely expressed in HL60 at the state of undifferentiation. It was also confirmed that the expression levels of CD11b were extremely low by immunobiological fluorescent imaging. Conversely, HL60s differentiated with 1 μM all-trans retinoic acid (ATRA), which is well known as a inducer of HL60 to neutrophil, were randomly adhered on the gaps, and only a few of the adhered HL60s moved onto the microband electrodes after 2nd patterning (day 4 inf Fig. B). The increase of number of cells remaining on the gaps in differentiated HL60 represented the upregulation of CD11b expression. The expression of CD11b in differentiated cells cultured in ATRA-containing medium for 4 days was confirmed by immunostaining. There was a good correlation between the expression levels of CD11b obtained by the present method and those obtained by conventional fluorescent method. In addition, the expression of CD13 was investigated using the device pretreated with anti-CD13. In this case, the majority of undifferentiated cells adhered on the gap between the microband electrode and the differentiated cells were expelled from the gap onto the microband electrode “b”. Thus, using the repulsive force of n-DEP to expel cells unbound to the substrate, the differentiation status can be elucidated in as little as 120 seconds. Figure 1

In Vitro Anticancer Effects of All-trans Retinoic Acid in Combination with Dacarbazine against CD117+ Melanoma Cells.

Malignant melanoma is a common form of skin cancer that contains different cell types recognized by various cell surface markers. Dacarbazine-based combination chemotherapy is frequently used for the treatment of melanoma. Despite its potent anticancer properties, resistance to dacarbazine develops in malignant melanoma. Here, we aim to improve response to dacarbazine therapy by pretreatment with all-trans retinoic acid (ATRA) in CD117+ melanoma cells. The CD117+ melanoma cells were sorted from A375 malignant melanoma cell line using magnetic-activated cell sorting (MACS). The cell viability was examined by cell proliferation assay (MTT). Apoptosis was determined by acridine orange/ ethidium bromide staining. Indeed, we performed flow cytometry to evaluate the cell cycle arrest. Here, the CD117+ melanoma cells were incubated with various concentrations of ATRA, dacarbazine, and their combination to determine IC50 values. We found that 20 µM ATRA treatment followed by dacarbazine was found to be more effective than dacarbazine alone. There was an indication that the combination of ATRA with dacarbazine (ATRA/dacarbazine) caused more apoptosis and necrosis in the melanoma cells (P<0.05). Furthermore, ATRA/dacarbazine treatment inhibited the cell at the G0/G1 phase, while dacarbazine alone inhibited the cells at S phase. Collectively, combined treatment with ATRA and dacarbazine induced more apoptosis and enhanced the cell cycle arrest of CD117+ melanoma cells. These results suggested that ATRA increased the sensitivity of melanoma cells to the effect of dacarbazine.

Impaired CPT1A Gene Expression Response to Retinoic Acid Treatment in Human PBMC as Predictor of Metabolic Risk.

Ex vivo human peripheral blood mononuclear cell (PBMC) systems offer the possibility to test transcriptomic effects of food bioactive compounds with potential health effects. We investigated all-trans retinoic acid (ATRA) effect on mRNA expression of key lipid metabolism and inflammatory genes in PBMCs from normal-weight (NW) and overweight-obese (OW-OB) men with different metabolic syndrome-related features. PBMCs were incubated with 10 µM ATRA and mRNA levels of selected genes were analyzed using real-time RT-qPCR. Human ex vivo PBMCs responded to ATRA treatment, but the response for some genes was dependent on body mass index (BMI), with a lower response in PBMC from OW-OB than from NW donors. Moreover, gene expression response was affected by circulating high-density lipoprotein (HDL)-cholesterol levels. Particularly, the response to ATRA of CPT1A, previously reported as a sensitive metabolic risk predictive biomarker, was dependent on HDL levels and not on BMI, being impaired in those individuals with lower HDL levels, specifically in OW-OB. Thus, PBMCs’ insensitivity to ATRA, which can be considered as indicative of impaired metabolism, was observed in individuals with higher metabolic risk (OW-OB with low HDL levels). In conclusion, an ex vivo human PBMC system indicates that ATRA response could be influenced by metabolic syndrome features. Moreover, our study reinforces the role of CPT1A as a marker of metabolic risk and points to plasmatic HDL-cholesterol levels as a parameter to take into consideration when the effects of nutritional factors and/or dietary interventions on humans are under study. Further studies including women are required to detect potential gender differences in the observed effects.

Cytotoxicity of SH-SY5Y Neuroblastoma Cells to the Antipsychotic Drugs, Chlorpromazine and Trifluoperazine, is via a Ca2+ -Mediated Apoptosis Process and Differentiation of These Cells with Retinoic Acid Makes Them More Resistant to Cell Death

Neuroblastomas usually occur in childhood and can have a relatively poor prognosis. Additionally, some antipsychotic drugs have been suggested to be neurotoxic, suggesting they might have therapeutic potential against neuronal cancer cells. In this study it was shown that 7 days treatment with 10 µM all-trans retinoic acid (ATRA) could alter SH-SY5Y (an undifferentiated neuroblastoma cell line) morphology in terms of neurite outgrowths and increased expression of the growth associated protein (GAP43), thus indicating that ATRA-treatment made these cells more differentiated in character. Next, a comparison of the effects of chlorpromazine and trifluoperazine, two types of typical first-generation antipsychotic drugs, on the cytotoxicity of both undifferentiated and ATRA-differentiated SH-SY5Y cells was undertaken. The results showed that both chlorpromazine and trifluoperazine, were highly cytotoxic to undifferentiated SH-SY5Y cells (LC50 values 5µM and 6µM, respectively). They were also deemed to be more selective towards neuronal cells compared to non-neuronal cells (COS7 cells). it was shown that cell death induced by chlorpromazine and trifluoperazine occurred mostly by Ca2+-mediated apoptosis. Furthermore, the cytotoxicity of chlorpromazine and trifluoperazine was decreased when the cells were differentiated with ATRA (LC50 values of 10.5µM and 12µM, respectively), indicating a possible therapeutic window for the potential use of chlorpromazine and trifluoperazine and potentially other FGAs in the treatment of neuroblastomas.

All-trans retinoic acid and human salivary histatin-1 promote the spreading and osteogenic activities of pre-osteoblasts invitro.

Cell‐based bone tissue engineering techniques utilize both osteogenic cells and biomedical materials, and have emerged as a promising approach for large‐volume bone repair. The success of such techniques is highly dependent on cell adhesion, spreading, and osteogenic activities. In this study, we investigated the effect of co‐administration of all‐trans retinoic acid (ATRA) and human salivary peptide histatin‐1 (Hst1) on the spreading and osteogenic activities of pre‐osteoblasts on bio‐inert glass surfaces. Pre‐osteoblasts (MC3T3‐E1 cell line) were seeded onto bio‐inert glass slides in the presence and absence of ATRA and Hst1. Cell spreading was scored by measuring surface areas of cellular filopodia and lamellipodia using a point‐counting method. The distribution of fluorogenic Hst1 within osteogenic cells was also analyzed. Furthermore, specific inhibitors of retinoic acid receptors α, β, and γ, such as ER‐50891, LE‐135, and MM‐11253, were added to identify the involvement of these receptors. Cell metabolic activity, DNA content, and alkaline phosphatase (ALP) activity were assessed to monitor their effects on osteogenic activities. Short‐term (2 h) co‐administration of 10 μm ATRA and Hst1 to pre‐osteoblasts resulted in significantly higher spreading of pre‐osteoblasts compared to ATRA or Hst1 alone. ER‐50891 and LE‐135 both nullified these effects of ATRA. Co‐administration of ATRA and Hst1 was associated with significantly higher metabolic activity, DNA content, and ALP activity than either ATRA or Hst1 alone. In conclusion, co‐administration of Hst1 with ATRA additively stimulated the spreading and osteogenicity of pre‐osteoblasts on bio‐inert glass surfaces in vitro.

All-trans retinoic acid suppressed GES-1 cell proliferation induced by exosomes from patients with precancerous lesions by arresting the cell cycle in S-phase.

We aimed to detect the expression of specific LncRNAs in exosomes isolated from the serum of patients with precancerous lesions and to study the effect of these serum exosomes on the activity of GES-1 cells in patients with precancerous lesions, as well as the activity of all-trans retinoic acid on GES-1 cells with or without the exosomes. Exosomes were extracted from the serum of patients with precancerous lesions and normal controls. Based on our previous sequencing results, quantitative real time-PCR was used to detect differentially expressed LncRNAs. Exosomes from the serum of patients with precancerous lesions were cocultured with GES-1 cells, and 5 μM all-trans retinoic acid was added as an intervention. Changes in cell viability and expression of LncHOXA10 were observed. Compared with the blank group, the proliferation activity of GES-1 cells cocultured with exosomes derived from the serum of patients with precancerous lesions was increased (P < 0.01), the proportion of cells in S phase was increased (P < 0.05). After adding 5 μM all-trans retinoic acid, the viability of cells decreased significantly (P < 0.01), the proportion of cells in S phase decreased significantly (P < 0.05). The expression of LncHOXA10 was decreased (P < 0.05). All-trans retinoic acid can conduct its chemopreventive effects by inhibiting the expression of LncHOXA10, thereby reducing the activity of LncHOXA10 in GES-1 cells cocultured with serum exosomes from patients with precancerous lesions.

The Antagonist of Retinoic Acid Receptor α, ER-50891 Antagonizes the Inhibitive Effect of All-Trans Retinoic Acid and Rescues Bone Morphogenetic Protein 2-Induced Osteoblastogenic Differentiation.

BackgroundHypervitaminosis A, alcoholism or medical treatment for acute promyelocytic leukaemia may cause unphysiologically high accumulation of all-trans retinoic acid (ATRA), which could inhibit osteoblastogenesis, thereby triggering osteoporosis. We have shown that bone morphogenetic protein-2 (BMP-2) can only partially antagonize the inhibitive effects of ATRA. In this study, we hypothesized that antagonists of retinoic acid receptors (RARs) could further antagonize the inhibitive effect of ATRA and rescue BMP2-induced osteoblastogenesis.Materials and MethodsWe first screened the dose-dependent effects of the specific antagonists of RAR α, β and γ and transforming growth factor-beta receptor (ER-50891, LE-135, MM11253, and SB-43142, respectively) on ATRA-induced inhibition of the total cell metabolic activity and proliferation of preosteoblasts. We selected ER-50891 and tested its effects on osteoblastogenesis with the presence or absence of 1 μM ATRA and/or 200 ng/mL BMP-2. We measured the following parameters: Alkaline phosphatase activity (ALP), osteocalcin (OCN) expression and extracellular matrix mineralization as well as the level of phosphorylated Smad1/5.ResultsER-50891 but not LE-135, MM11253, or SB-431542 significantly antagonized the inhibition of ATRA and enhanced the total cell metabolic activity and proliferation of preosteoblasts. Dose-dependent assays show ER-50891 could also rescue ATRA inhibited OCN expression and mineralization with or without the induction of BMP. ER-50891 also suppressed the ALP activity that was synergistically enhanced by BMP and ATRA. Neither ATRA, nor ER-50891 or their combination significantly affected the level of BMP-induced phosphorylated Smad1/5.ConclusionThe antagonist of RARα, ER-50891 could significantly attenuate ATRA’s inhibitive effects on BMP 2-induced osteoblastogenesis.

Treating TB human neuroectodermal cell line with retinoic acid induces the appearance of neuron-like voltage-gated ionic currents

TB is a cell line derived from the cerebrospinal fluid sample of a patient with primary leptomeningeal melanomatosis. Our previous immunological and ultrastructural analysis revealed that TB cells differentiate towards a neuronal phenotype when grown in vitro up to 7 days in presence of 10 µM all-trans retinoic acid (RA). Recently, we reported that TB cells are sensitive to the cytotoxic effects of β-amyloid peptides, activating the cytosolic phospholipase A2. To date, it is not known if RA, in addition to inducing morphological changes, also causes functional modification in TB cells, by regulating voltage-gated ionic currents. To this purpose, we performed electrophysiological characterization of undifferentiated (TB) and differentiated (RA-TB) cells by means of whole-cell patch clamp recordings. Upon depolarizing stimuli, both groups displayed voltage-gated K+ outward currents of similar amplitude. By contrast, the low amplitude voltage-gated Na+ currents recorded in undifferentiated TB cells were largely up-regulated by RA exposure. This current was strongly reduced by TTX and lidocaine and completely abolished by removal of extracellular sodium. Furthermore, treatment with RA caused the appearance of a late-onset inward current carried by Ca2+ ions in a subpopulation of TB cells. This current was not affected by removal of extracellular Na+ and was completely blocked by Cd2+, a broad-spectrum blocker of Ca2+ currents. Altogether, our results indicate that RA-differentiation of TB cells induces functional changes by augmenting the amplitude of voltage-gated sodium current and by inducing, in a subpopulation of treated cells, the appearance of a voltage-gated calcium current.

The Genes for Tissue Factor F3 and Nuclear Receptor 4A Are Down-Regulated in Early Death Acute Promyelocytic Leukemia Patients

Introduction: Acute promyelocytic leukemia (APL) patients are successfully treated via differentiation therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). Attempts to apply ATRA-based differentiation therapy to non-APL acute myeloid leukemia (AML) patients have not been effective so far (Johnson & Redner, 2015). Furthermore, 10-30% of the APL patients suffer an early death (ED) within 30 days, due to hemorrhages, infections, differentiation syndrome and thrombosis. Different risk factors have been identified, but the underlying mechanisms and successful treatment of ED in APL patients still have not been established (Kwaan et al., 2014, Lehmann et al., 2017). Hence, it is highly important to identify novel risk factors to understand the mechanistic processes in APL ED patients.Methods: To identify target genes, 50 bp single-read RNA sequencing (RNAseq) of 6 ED and 9 APL controls (cohort #1; n=15) and 4 ED and 5 APL controls (cohort #2; n=9) was executed. Samples were taken from patients with confirmed diagnosis of APL before beginning of treatment. Cohort #1 consisted of 15 patients: median age 60 years (range 37-73 years), 10 high-risk patients and 5 low/intermediate-risk patients according to Sanz score. Patients of cohort #1 were treated according to the AIDA2000 protocol of the Study Alliance Leukemia (SAL) study group. Cohort #2 consisted of 9 patients: median age 55 years (range 36-79 years), 4 high-risk patients and 5 low/intermediate-risk patients. Most patients of cohort 2 were treated according to the AIDA2000 (SAL) or APL0406 protocol. Gene validation was performed via RT-qPCR. PML-RARα variants were determined by Mentype AMLplexQS (Biotype). Survival and RT-qPCR analyses were performed with 64 non-APL AML patients´ samples treated within the clinical trial of the AMLSG HD98B study (Schlenk et al., 2004). In this trial, all patients received ICE (idarubicin, cytarabine, etoposide) chemotherapy. The patients were randomly assigned to ATRA or no ATRA. In our cohort, 26 patients had received ICE-ATRA, whereas 38 only ICE. Amaxa nucleofector technology was used for overexpression of PML-RARα bcr1 or bcr3 variant in U937 cells. NB4 or AML cells treated with 1 µM ATRA up to 72 h or 1-2 µM ATO up to 48 h were analyzed via flow cytometry, CellTiter-Glo viability assay, RT-qPCR or Western blot.Results: RNAseq of cohorts 1 and 2 showed F3 (Tissue Factor) and members of nuclear receptor 4A family, NR4A1/2/3, significantly downregulated in ED compared to control APL cases. GSEA analysis further identified a gene family including F3 and members of nuclear receptor 4A family, NR4A1/2/3, co-regulated upon leukotriene and thrombin treatment. Downregulation of F3 was further validated by RT-qPCR. Analysis of PML-RARα variants in APL control and ED cases (n=38, Chi-square p < 0.041) showed a significant enrichment of the short variant bcr3 in ED APL. Artificial overexpression of the short bcr3 and long bcr1 PML/RARα variant in U937 further revealed a correlation between bcr3 and downregulation of NR4A2/3. Moreover, treatment of the APL NB4 cell line with ATRA or ATO induced further downregulation of F3 but upregulation of NR4A2/3 transcripts. ATRA treatment induced the same effects on F3 and NR4A3 protein levels, while ATO led not only to a decrease of F3 but also NR4A3 protein levels.We next sought to address the role of F3 and NR4A in non-APL AML. In 5 non-APL AML cell lines high F3 transcript and protein levels were positively correlated with a better response to ATRA treatment in vitro. Consistently, analyzing samples taken from the AMLSG HD98B trial, AML patients with high F3 but also NR4A3 transcript levels treated with ICE chemotherapy showed a significantly prolonged overall survival upon additional ATRA treatment in vivo (Log-rank p < 0.008).Conclusions: Expression of F3 and NR4A1/2/3 is downregulated in APL ED and decreased expression of NR4A2/3 is associated with short PML-RARα variant bcr3, which is significantly enriched in ED APL. Since NR4A members are associated with coagulation and inflammation, they may be important F3-related factors, contributing to the bcr3 ED APL phenotype. As ATRA and ATO treatment is known to further inhibit F3 expression, alternative therapies not inhibiting F3 expression could be worthwhile in APL ED patients. Moreover, F3 and NR4A3 expression levels seem to be highly relevant as marker for the prediction of ATRA response in non-APL AML patients. [Display omitted] DisclosuresPlatzbecker:Celgene: Research Funding. Thiede:Novartis: Honoraria, Research Funding; AgenDix: Other: Ownership. Schlenk:Pfizer: Research Funding, Speakers Bureau.

All-trans retinoic acid can antagonize osteoblastogenesis induced by different BMPs irrespective of their dimerization types and dose-efficiencies.

IntroductionAlcoholism can lead to low mineral density, compromised regenerative bone capacity and delayed osteointegration of dental implants. This may be partially attributed to the inhibitive effect of all-trans retinoic acid (ATRA), a metabolite of alcohol, on osteoblastogenesis. Our previous studies demonstrated that heterodimeric bone morphogenetic protein 2/7 (BMP2/7) was a more potent BMP than homodimeric BMP2 or BMP7, and could antagonize the inhibitive effect of ATRA to rescue osteoblastogenesis.Materials and methodsIn this study, we compared the effectiveness of BMP2/7, BMP2 and BMP7 in restoring osteoblastogenesis of murine preosteoblasts upon inhibition with 1 µM ATRA, and we further analyzed the potential mechanisms. We measured the following parameters: cell viability, ALP, OCN, mineralization, the expression of osteogenic differentiation marker genes (Collagen I, ALP and OCN) and the expression of BMP signaling key genes (Dlx5, Runx2, Osterix and Smad1).ResultsBMP2/7 treatment alone induced significantly higher osteoblastogenesis compared to BMP2 and BMP7. When cells were treated by ATRA, BMP2/7 was superior only in rescuing cell viability and ALP activity, compared to BMP2 or BMP7. However, BMP2/7 was not superior to BMP2 or BMP7 in restoring OCN expression and extracellular mineralized nodules, or in rescuing expression of two key osteogenic genes, Dlx5 and Runx2. Irrespective of their dimeric types or potency, the selected BMPs could antagonize the inhibitory effect of ATRA on osteoblastogenesis.ConclusionThe presence of ATRA, BMP2/7 still induced significantly higher cell viability and early differentiation than the homodimers. However, ATRA significantly attenuated the advantages of BMP2/7 in inducing late and final osteoblastogenic differentiation over the homodimers.

Upregulation of CD54 and downregulation of HLA‑ABC contribute to the novel enhancement of the susceptibility of HL-60 cells to NK cell-mediated cytolysis induced by ATRA plus VPA.

Enhancement of the susceptibility of HL-60 cells to NK cell-mediated cytolysis induced by all-trans-retinoic acid (ATRA) plus valproate (VPA) was evaluated. In addition to the synergistic effect of ATRA plus VPA on HL-60 cells, the optimal concentration of 1mM VPA plus 0.5µM ATRA increased the cytotoxic sensitivity of HL-60 cells to NK cells. The expression of the activated receptors NKp30 and NKG2D on NK-92 cells was higher compared with the levels noted for the other receptors, and the expression of NKG2D ligands MICA/B on HL-60 cells was not significantly upregulated in the ATRA plus VPA goup compared with the control. Moreover, it was observed that the ligands of NKp30 on HL-60 cells presented the same variation trend. As to the co-stimulatory and adhesion molecules on NK-92 and their ligands on HL-60 cells post exposure to ATRA and VPA alone or their combination, there was no obvious change in the expression of CD112, CD48 and CD70 on the HL-60 cells. However, the expression of CD54 on HL-60 cells was significantly upregulated. In contrast, the expression of NKG2A ligands HLA-ABC on HL-60 cells was obviously downregulated. In addition, the expression of HLA-E on the HL-60 cells in the group treated with ATRA plus VPA was not significantly increased. In conclusion, the combination of VPA and ATRA not only induced the differentiation of HL-60 cells, but also induced enhancement of the sensitivity of HL-60 cells to NK cells by downregulating the expression of HLA-ABC and upregulating the expression of CD54, but not MICA/MICB. The results provide experimental and theoretical basis for the clinical combination of a low-dose of ATRA plus VPA for the treatment of leukemia.

Abstract 1189: Combination treatments with retinoic acid and the synthetic retinoid ST1926 in 2D and 3D breast cancer models overcome retinoic acid resistance and eradicate breast cancer stem/progenitor cells

Abstract Despite recent advances in breast cancer therapy, achieving complete remission in metastatic breast cancer patients remains a challenge. Retinoids are crucial regulators of cellular proliferation, differentiation, and cell death, and have shown potent chemotherapeutic and chemopreventive properties. The major drawback of the use of all-trans retinoic acid (ATRA) in cancer therapy is acquired resistance. Therefore, synthetic retinoids such as ST1926 emerged as potent anti-cancer agents. Here, we investigated the anti-tumor activities of ATRA, ST1926, and their combination treatments in 2D and 3D human breast cancer models and their targeting of breast cancer stem cells (CSCs)/progenitor cells. We have shown that in 2D culture models, MCF-7 and MDA-MB-231 cells are resistant to ATRA while being sensitive to ST1926 at sub-micromolar (μM) concentrations in an irreversible manner. Importantly, ST1926 had no effect on the ‘normal-like’ MCF-10A breast epithelial cells. ST1926 induced massive apoptosis in MCF-7 cells and it resulted in S-phase arrest and necrosis in the triple negative and metastatic MDA-MB-231 cells. Furthermore, ST1926 caused early DNA damage, increased the expression of the tumor suppressors p53 and p21, downregulated the Wnt/β-catenin pathway, and modulated the expression levels of the different retinoid receptors. Interestingly, combination treatments as low as 0.1 μM ST1926 and 0.5 μM ATRA synergistically inhibited the proliferation in 2D models of MCF-7 and MDA-MB-231 cells, independently of retinoid receptor signaling, while sparing the normal breast epithelial cells. Anchorage-independent growth of MCF-7 and MDA-MB-231 cells was examined using the soft agar colony formation assay where sub-μM concentrations of ST1926 or μM concentrations of ATRA were shown to reduce the size and the number of breast cancer colonies. ST1926 drastically induced cell death in 3D Matrigel ‘on-top’ assay cultures of breast cancer cells while the lumen of the normal-like breast epithelial cell line S1 was maintained. Finally, treatment with 0.01 μM ST1926 alone or 0.001 μM ST1926 in combination with 0.1 μM ATRA abrogated sphere formation and the self-renewal ability of breast CSCs in the 3D sphere formation assay. In summary, ST1926, ATRA, and their combination treatments were shown to display more potent anti-tumor properties in 3D versus 2D human breast cancer models. Our results also demonstrate the therapeutic potential of ST1926 in sensitizing breast cancer cells to ATRA and in targeting the population of breast CSCs. As 3D culture models are more representative of the tumor microenvironment and serve as valid tools in drug discovery, our results highlight the promising use of ATRA/ST1926 combinations in metastatic and triple negative breast cancers. Citation Format: Patrick Aouad, Melody Saikali, Rana Abdel-Samad, Leeanna El–Houjeiri, Claudio Pisano, Rabih Talhouk, Nadine Darwiche. Combination treatments with retinoic acid and the synthetic retinoid ST1926 in 2D and 3D breast cancer models overcome retinoic acid resistance and eradicate breast cancer stem/progenitor cells. [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 1189.