Project description:NR4A1 (Nur77, TR3) is an orphan nuclear receptor that is overexpressed in pancreatic cancer cells and tumors and exhibits pro-oncogenic activity. Knockdown of NR4A1 by RNA interference (siNR4A1) in Panc1 cells and analysis of the proteome resulted in induction of several markers of endoplasmic reticulum (ER) stress including glucose-related protein 78 (GRP78), CCAAT/enhancer-binding protein-homologous protein (CHOP), activating transcription factor-3 (ATF-3) and AFT-6. These effects were accompanied by induction of apoptosis and similar results were observed after treatment of pancreatic cancer cells with the known inactivator of NR4A1, 1,1-bis(3’-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH). Both siNR4A1 (transfected) and DIM-C-pPhOH also induced reactive oxygen species (ROS) and induction of ROS and ER stress by these agents was attenuated after cotreatment with antioxidants. Transfection of Panc1 cells with siNR4A1 follow by analysis of gene expression by arrays identified ROS metabolism genes regulated by NR4A1. Knockdown of one of these genes, thioredoxin domain containing 5 (TXNDC5) also resulted in induction of ROS and ER stress demonstrating that NR4A1 regulates levels of ER stress and ROS in pancreatic cancer cells to facilitate cell proliferation and survival. Inactivation of this receptor by siNR4A1 or DIM-C-pPhOH decreases TXNDC5 resulting in activation of ROS/ER stress and pro-apoptotic pathways and represents a novel pathway for inducing cell death in pancreatic cancer cells. Two groups of samples are included: 1. siControl; 2. siNR4A1 treatment in PAC1 cell. Transfection of Panc1 cells with siNR4A1 follow by analysis of gene expression by arrays identified ROS metabolism genes regulated by NR4A1.
Project description:Danazol binds directly to the orphan nuclear receptor NR4A1, activates telomerase, and induces unique transcriptomic changes in cellular response to stresses, including metabolic strain and immune response
Project description:NR4A1 (Nur77, TR3) is an orphan nuclear receptor that is overexpressed in pancreatic cancer cells and tumors and exhibits pro-oncogenic activity. Knockdown of NR4A1 by RNA interference (siNR4A1) in Panc1 cells and analysis of the proteome resulted in induction of several markers of endoplasmic reticulum (ER) stress including glucose-related protein 78 (GRP78), CCAAT/enhancer-binding protein-homologous protein (CHOP), activating transcription factor-3 (ATF-3) and AFT-6. These effects were accompanied by induction of apoptosis and similar results were observed after treatment of pancreatic cancer cells with the known inactivator of NR4A1, 1,1-bis(3’-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH). Both siNR4A1 (transfected) and DIM-C-pPhOH also induced reactive oxygen species (ROS) and induction of ROS and ER stress by these agents was attenuated after cotreatment with antioxidants. Transfection of Panc1 cells with siNR4A1 follow by analysis of gene expression by arrays identified ROS metabolism genes regulated by NR4A1. Knockdown of one of these genes, thioredoxin domain containing 5 (TXNDC5) also resulted in induction of ROS and ER stress demonstrating that NR4A1 regulates levels of ER stress and ROS in pancreatic cancer cells to facilitate cell proliferation and survival. Inactivation of this receptor by siNR4A1 or DIM-C-pPhOH decreases TXNDC5 resulting in activation of ROS/ER stress and pro-apoptotic pathways and represents a novel pathway for inducing cell death in pancreatic cancer cells.
Project description:A 4.1 μs molecular dynamics simulation of the NR4A1 (hNur77) apo-protein has been undertaken and a previously undetected druggable pocket has become apparent that is located remotely from the 'traditional' nuclear receptor ligand-binding site. A NR4A1/bis-indole ligand complex at this novel site has been found to be stable over 1 μs of simulation and to result in an interesting conformational transmission to a remote loop that has the capacity to communicate with a NBRE within a RXR-α/NR4A1 heterodimer. Several features of the simulations undertaken indicate how NR4A1 can be affected by alternate-site modulators.
Project description:Piperlongumine and derivatives are being developed as anticancer agents which act primarily as inducers of reactive oxygen species (ROS) in cancer cell lines. Many of the anticancer activities of piperlongumine resemble those observed for bis-indole derived compounds that bind the orphan nuclear receptor 4A1 (NR4A1) and act as inverse receptor agonists to inhibit NR4A1-regulated pro-oncogenic pathways and genes. In this study we show that like other NR4A1 inverse agonists piperlongumine inhibited RKO, SW480 and HCT116 colon cancer cell growth migration and invasion and induced apoptosis. Piperlongumine also downregulated the pro-reductant isocitrate dehydrogenase 1 (IDH1) and thioredoxin domain-containing 5 (TXNDC5) gene products resulting in the induction of ROS as previously observed for other inverse NR4A1 agonists. ROS also induced sestrin2 and this resulted in activation of AMPK phosphorylation and inhibition of mTOR pathway signaling. It has previously been reported that these pathways/genes are also regulated by inverse NR4A1 agonists or by knockdown of NR4A1. We also observed that piperlongumine directly bound NR4A1, inhibited NR4A1-dependent transactivation and interactions of the NR4A1/Sp1 complex bound to the GC-rich promoter of the NR4A1-regulated G9a gene.
Project description:NR4A1 acts as an oncogene and plays an important role in colorectal cancer development and progression, but little is known about the regulatory mechanism of NR4A1 expression. MicroRNA (miRNA) is involved in the progression of various tumors, affecting proliferation, apoptosis or migration. We aimed to elucidate whether miRNA regulates NR4A1 expression and determine its underlying significance in colorectal cancer. By using the TargetScan database, we identified a miR-506 binding site in the NR4A1 3'-UTR. Examination of colorectal cancer tissues and cells revealed that NR4A1 mRNA and protein were up-regulated, while miR-506 expression was down-regulated. Spearman correlation analysis revealed that expression of NR4A1 mRNA was negatively correlated with miR-506 levels in colorectal cancer tissue. Further studies indicated that miR-506 decreased NR4A1 expression through directly targeting the NR4A1 mRNA 3'-UTR. Functional experiments showed that rescue of NR4A1 expression in cells reversed the inhibitory effects of miR-506 on proliferation, migration and invasion of colorectal cancer cells. In conclusion, miR-506 acts as a tumor suppressor and inhibits proliferation, migration and invasion in colorectal cancer cells partly through decreasing NR4A1 expression.
Project description:It was recently reported that the hydroxyflavones quercetin and kaempferol bind the orphan nuclear receptor 4A1 (NR4A1, Nur77) and act as antagonists in cancer cells and tumors, and they inhibit pro-oncogenic NR4A1-regulated genes and pathways. In this study, we investigated the interactions of flavone, six hydroxyflavones, seven dihydroxyflavones, three trihydroxyflavones, two tetrahydroxyflavones, and one pentahydroxyflavone with the ligand-binding domain (LBD) of NR4A1 using direct-binding fluorescence and an isothermal titration calorimetry (ITC) assays. Flavone and the hydroxyflavones bound NR4A1, and their KD values ranged from 0.36 µM for 3,5,7-trihydroxyflavone (galangin) to 45.8 µM for 3'-hydroxyflavone. KD values determined using ITC and KD values for most (15/20) of the hydroxyflavones were decreased compared to those obtained using the fluorescence assay. The results of binding, transactivation and receptor-ligand modeling assays showed that KD values, transactivation data and docking scores for these compounds are highly variable with respect to the number and position of the hydroxyl groups on the flavone backbone structure, suggesting that hydroxyflavones are selective NR4A1 modulators. Nevertheless, the data show that hydroxyflavone-based neutraceuticals are NR4A1 ligands and that some of these compounds can now be repurposed and used to target sub-populations of patients that overexpress NR4A1.
Project description:Hematopoietic stem cells (HSCs) sustain life-long hematopoiesis and emerge during mid-gestation from hemogenic endothelial (HE) progenitors via an endothelial to hematopoietic transition (EHT). The full scope of molecular mechanisms governing this process remains unclear. The NR4A subfamily of orphan nuclear receptors act as tumour suppressors in myeloid leukemogenesis and have never been implicated in HSC specification. Here, we report that Nr4a1 and Nr4a2 expression is upregulated in hemogenic endothelium during EHT. Progressive genetic ablation of Nr4a gene dosage results in a gradual decrease in numbers of nascent c-Kit+ hematopoietic progenitors in developing embryos, c-Kit+ cell cluster size in the dorsal aorta, and a block in HSC maturation, revealed by an accumulation of pro-HSCs and pre-HSC-type I cells and decreased numbers of pre-HSC-type II cells. Consistent with these observations, cells isolated from E11.5 Nr4a1-/-; Nr4a2-/- aorta-gonads-mesonephros (AGM) are devoid of in vivo long-term hematopoietic repopulating potential. Molecularly, employing spatial transcriptomic analysis we determined that the genetic ablation of Nr4a1 and Nr4a2 prevents NOTCH signaling from being downregulated in intra-aortic clusters and thus for pro-HSCs to mature into HSCs. Interestingly, this defect is partially rescued via ex vivo culture of dissected AGMs with SCF, IL3 and FLT3L, which may bypass NOTCH-dependent regulation. Overall, our data reveal a novel role for the NR4A family of orphan nuclear receptors in EHT.