Gadd45a mRNA Research Articles

Piperlongumine inhibits antioxidant enzymes, increases ROS levels, induces DNA damage and G2/M cell cycle arrest in breast cell lines

ABSTRACT Piperlongumine (PLN) is a biologically active alkaloid/amide derived from Piper longum, with known promising anticancer activity. The aim of this study was to compare the antiproliferative activity of PLN in human breast MCF-7 adenocarcinoma cell line with effects in HB4a normal mammary epithelial non-tumor cell line. The parameters examined were cell growth, viability, reactive oxygen species (ROS) levels and DNA damage, as well as the effects on the modulating targets responsible through regulation of these pathways. PLN increased ROS levels and expression of the SOD1 antioxidant enzyme. PLN inhibited the expression of the antioxidant enzymes catalase, TRx1, and PRx2. The ability of PLN to inhibit antioxidant enzyme expression was associated with the oxidative stress response. PLN induced genotoxicity in both cell lines and upregulated the levels of GADD45A mRNA and p21 protein. The DNA damage response ATR protein was downregulated in both cell lines and contributed to an enhanced PLN genotoxicity. In HB4a cells, Chk1 protein, and mRNA levels were also decreased. In response to elevated ROS levels and DNA damage induction, the cells were arrested at the G2/M phase, probably in an attempt to promote cell survival. Although cell viability was reduced in both cell lines, only HB4a cells underwent apoptotic cell death, whereas other types of cellular death may be involved in MCF-7 cells. Taken together, these data provide insight into the anticancer mechanisms attributed to PLN effects, which acts as an inhibitor of DNA damage response (DDR) proteins and antioxidant enzymes.

IRE1-mediated degradation of pre-miR-301a promotes apoptosis through upregulation of GADD45A

The unfolded protein response is a survival signaling pathway that is induced during various types of ER stress. Here, we determine IRE1’s role in miRNA regulation during ER stress. During induction of ER stress in human bronchial epithelial cells, we utilized next generation sequencing to demonstrate that pre-miR-301a and pre-miR-106b were significantly increased in the presence of an IRE1 inhibitor. Conversely, using nuclear-cytosolic fractionation on ER stressed cells, we found that these pre-miRNAs were decreased in the nuclear fractions without the IRE1 inhibitor. We also found that miR-301a-3p targets the proapoptotic UPR factor growth arrest and DNA-damage-inducible alpha (GADD45A). Inhibiting miR-301a-3p levels or blocking its predicted miRNA binding site in GADD45A’s 3’ UTR with a target protector increased GADD45A mRNA expression. Furthermore, an elevation of XBP1s expression had no effect on GADD45A mRNA expression. We also demonstrate that the introduction of a target protector for the miR-301a-3p binding site in GADD45A mRNA during ER stress promoted cell death in the airway epithelial cells. In summary, these results indicate that IRE1’s endonuclease activity is a two-edged sword that can splice XBP1 mRNA to stabilize survival or degrade pre-miR-301a to elevate GADD45A mRNA expression to lead to apoptosis.9J7o_YRPucfgg8rDu5QLJgVideo

BBOX1-AS1 mediates trophoblast cells dysfunction via regulating hnRNPK/GADD45A axis†.

Recurrent pregnancy loss (RPL) is a common pathological problem during pregnancy, and its clinical etiology is complex and unclear. Dysfunction of trophoblasts may cause a series of pregnancy complications, including preeclampsia, fetal growth restriction, and RPL. Recently, lncRNAs have been found to be closely related to the occurrence and regulation of pregnancy-related diseases, but few studies have focused on their role in RPL. In this study, we identified a novel lncRNA BBOX1-AS1 that was significantly upregulated in villous tissues and serum of RPL patients. Functionally, BBOX1-AS1 inhibited proliferation, migration, invasion, tube formation and promoted apoptosis of trophoblast cells. Mechanistically, overexpression of BBOX1-AS1 activated the p38 and JNK MAPK signaling pathways by upregulating GADD45A expression. Further studies indicated that BBOX1-AS1 could increase the stability of GADD45A mRNA by binding hnRNPK and ultimately cause abnormal trophoblast function. Collectively, our study highlights that the BBOX1-AS1/hnRNPK/GADD45A axis plays an important role in trophoblast-induced RPL and that BBOX1-AS1 may serve as a potential target for the diagnosis of RPL.

AD80, a multikinase inhibitor, as a potential drug candidate for colorectal cancer therapy

AimsColorectal cancer (CRC) is a very heterogeneous disease. One of its hallmarks is the dysregulation of protein kinases, which leads to molecular events related to carcinogenesis. Hence, kinase inhibitors have been developed and are a new strategy with promising potential for CRC therapy. This study aims to explore AD80, a multikinase inhibitor, as a drug option for CRC, with evaluation of the PI3K/AKT/mTOR and MAPK (ERK1/2) status of CRC cells' panel and the cytotoxicity of AD80 in those cells, as well as in normal colon cells. Main methodsCellular and molecular mechanisms, such as clonogenicity, cell cycle, morphology, protein and mRNA expression, were investigated in CRC cells after AD80 exposure. Key findingsResults show that PI3K/AKT/mTOR and MAPK signaling pathways are upregulated in CRC cellular models, with increased phosphorylation of mTOR, P70S6K, S6RP, 4EBP1, and ERK1/2. Hence, AD80 selectively reduces cell viability of CRC cells. Therefore, the antitumor mechanisms of AD80, such as clonogenicity inhibition (reduction of colony number and size), G2/M arrest (increased G2/M population, and CDKN1B mRNA expression), DNA damage (increased H2AX and ERK1/2 phosphorylation, and CDKN1A and GADD45A mRNA expression), apoptosis (increased PARP1 cleavage, and BAX, PMAIP1, BBC3 mRNA expression) and inhibition of S6RP phosphorylation were validated in CRC model. SignificanceOur findings reinforce kinases as promising cancer therapeutic targets for the treatment of colorectal cancer, suggesting AD80 as a drug candidate.

Abstract 2444: Do all 4 NCL RNA Binding Domains play a role in mRNA target specificity? An in silico study to decipher NCL-mRNA interactions

Abstract RNA binding proteins (RBPs) are post-transcriptional regulators that associate with RNA molecules through one or more of their RNA-binding domains (RBDs). The dysregulation of RBPs, and the RNA metabolism pathways they intersect, are known drivers of tumorigenesis. Nucleolin (NCL) is a stress responsive RBP with four RBDs that directly impacts gene expression by altering rRNA processing, RNA localization, miRNA biogenesis, mRNA decay, and translation. NCL is known to interact with both the 3' and 5' untranslated regions (UTR) and coding regions of target mRNAs to either modulate their stability or translation via recognition of AU-rich or G-rich elements in the RNA. However, the consequences of NCL-mRNA interactions are target-specific as well as context and location dependent. While NCL interacts with both 3' and 5' UTR of TP53 mRNA and suppresses its translation, interactions of NCL with 5' UTR of an anti-apoptotic gene, BCL2, stabilizes this transcript. NCL-mediated enhanced biogenesis of tumorigenic mir-15a and mir-16, on the other hand, results in the translational repression of BCL2. Because NCL exerts its functions in such a complex manner, elucidation of its roles in tumorigenic pathways is paramount in the development of therapeutical applications targeting NCL-RNA interactions. Mechanisms driving NCL-mRNA interactions are currently unknown and this knowledge gap is further compounded by the incomplete nature of the current structural information for NCL and its mRNA targets. In this study, we aim to elucidate NCL RBD-mRNA interactions using computational tools. We investigated interactions of NCL with a specific subset of mRNAs that are implicated in breast cancer progression. We have previously generated and validated in silico models for all the four NCL-RBDs (1-4) in various combinations. Using several secondary and tertiary structure prediction programs along with structure refinement programs, we have generated 3D models of TP53, BCL2, CSF-1, and GADD45α mRNA UTR molecules. Our docking analyses suggests that RBD1-2 and RBD3-4 collaborate in most NCL-mRNA interactions using RNA binding motifs (RNP1 & RNP2) on NCL. We further identify additional contact points in the bridging linker regions between the RBDs that might be crucial for the structural stability of these complexes. This study provides details previously not reported in the literature and provides a comprehensive map of NCL RBD-mRNA interactions that have direct pathophysiological relevance in breast cancer. Altered levels of NCL expression are linked with poor prognosis in breast cancers and targeting NCL results in a better survival outcome. Understanding how NCL associates with its mRNA targets will reveal binding pockets and hence potential sites for drug interventions in addition to characterizing the complex nature of NCL-mRNA interactions/specificity in multiple cancer types. Citation Format: Avdar San, Anjana Saxena, Shaneen Singh. Do all 4 NCL RNA Binding Domains play a role in mRNA target specificity? An in silico study to decipher NCL-mRNA interactions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2444.

GADD45\u03b1 drives brown adipose tissue formation through upregulating PPAR\u03b3 in mice

Stress can lead to obesity and metabolic dysfunction, but the underlying mechanisms are unclear. Here we identify GADD45α, a stress-inducible histone folding protein, as a potential regulator for brown adipose tissue biogenesis. Unbiased transcriptomics data indicate a positive correlation between adipose Gadd45a mRNA level and obesity. At the cellular level, Gadd45a knockdown promoted proliferation and lipolysis of brown adipocytes, while Gadd45a overexpression had the opposite effects. Consistently, using a knockout (Gadd45a−/−) mouse line, we found that GADD45α deficiency inhibited lipid accumulation and promoted expression of thermogenic genes in brown adipocytes, leading to improvements in insulin sensitivity, glucose uptake, energy expenditure. At the molecular level, GADD45α deficiency increased proliferation through upregulating expression of cell cycle related genes. GADD45α promoted brown adipogenesis via interacting with PPARγ and upregulating its transcriptional activity. Our new data suggest that GADD45α may be targeted to promote non-shivering thermogenesis and metabolism while counteracting obesity.

Altered amygdala DNA methylation mechanisms after adolescent alcohol exposure contribute to adult anxiety and alcohol drinking

Binge drinking during adolescence increases the risk for neuropsychiatric disorders including alcoholism in adulthood. DNA methylation in post-mitotic neurons is an important epigenetic modification that plays a crucial role in neurodevelopment. We examined the effects of intermittent ethanol exposure during adolescence on adult behavior and whether DNA methylation changes provide a plausible explanation for the lasting effects of this developmental insult. One hour after last adolescent intermittent ethanol (AIE), growth arrest and DNA damage inducible protein 45 (Gadd45a, Gadd45b, and Gadd45g) mRNA expression was increased and DNA methyltransferase (DNMT) activity and Dnmt3b expression was decreased in the amygdala as compared to adolescent intermittent saline (AIS) rats. However, AIE rats 24 h after last exposure displayed increased DNMT activity but normalized Gadd45 and Dnmt3b mRNA expression compared to AIS rats. In adulthood, rats exposed to AIE show increased Dnmt3b mRNA expression and DNMT activity, along with decreased Gadd45g mRNA expression in the amygdala. DNA methylation of neuropeptide Y (Npy) and brain-derived neurotrophic factor (Bdnf) exon IV is increased in the AIE adult amygdala compared to AIS adult rats. Treatment with the DNMT inhibitor 5-azacytidine (5-azaC) at adulthood normalizes the AIE-induced DNA hypermethylation of Npy and Bdnf exon IV with concomitant reversal of AIE-induced anxiety-like and alcohol-drinking behaviors. These results suggest that binge-like ethanol exposure during adolescence leads to dysregulation in DNA methylation mechanisms in the amygdala which may contribute to behavioral phenotypes of anxiety and alcohol use in adulthood.

Chemical Composition and Antiproliferative Effects of a Methanol Extract of Aspongopus chinensis Dallas.

Natural products from insects can be potent sources for developing a variety of pharmaceutical products. Aspongopus chinensis Dallas has been used as a traditional Chinese medicine and there are several clinical evidences to support its anticancer activity. However, the anticancer active ingredients present in A. chinensis remain unidentified. In the present study, we investigated the anticancer effects of a methanol extract of A. chinensis (AME). Gas chromatography mass spectrometry was used to analyse the chemical composition of AME. The cell viability of MDA-MB-453 and HCC-1937 cells treated with different concentrations of AME was detected by MTT assay and the ratio of cells in different cell cycle phases was analysed by flow cytometry. The expression of genes associated with cell cycle was analysed by real-time PCR assay. The results showed that oleic acid (25.39%) and palmitic acid (21.798%) are the main anticancer compounds present in AME. There was a concentration-dependent decrease in the proliferation of MDA-MB-453 and HCC-1937 cells. Moreover, treatment with AME induced a S-phase arrest in the cells. Real-time PCR assay demonstrated that AME could significantly downregulate the expression of CDC20, AURKB, PLK1, CCNB2, and TOP2A mRNAs and upregulate the expression of GADD45A mRNA. We demonstrate that the methanol extract of A. chinensis could be a potential natural alternative or complementary therapy for breast cancer.

Exercise preconditioning attenuates hind limb unloading-induced gastrocnemius muscle atrophy possibly via the HDAC4/Gadd45 axis in old rats.

The mechanisms involved in unloading-induced skeletal muscle loss may be age-specific, and the evidence for exercise preconditioning-induced protection against disuse muscle atrophy in aged rats is limited. Therefore, in this study, we investigated age-related differences in the activation of the HDAC4/Gadd45α pathway following hindlimb unloading (HU). We also assessed the protective effect of preconditioning exercise on this pathway in young and old rat gastrocnemius muscle. Three-month-old (young, n = 18) and 24-month-old (old, n = 18) male Wistar rats were assigned to the following groups: control group (n = 6), seven days of HU group (n = 6), and a bout of exercise preconditioning prior to HU (Ex+HU) group (n = 6). Rats of both ages in the Ex + HU group ran continuously on a motor-driven treadmill (0° slope, 20 m/min, 15 min) prior to HU. The gastrocnemius muscles were removed after 7 days of HU and analyzed for protein content and mRNA expression. Gastrocnemius muscle weight was significantly higher in the Ex+HU group than in the HU group of old rats, but not in young rats. Levels of HDAC4 protein and mRNA were significantly increased in the old HU group. However, the increase was significantly suppressed in the old Ex+HU group. Moreover, the protective effect of exercise preconditioning had a positive effect on Gadd45α mRNA and protein levels only in the old Ex+HU group. No exercise preconditioning-related protection was observed in the young rats. Our data indicated that a single bout of preconditioning exercise prior to HU may exert a protective effect in disuse muscle atrophy in old rats and that these effects may be partially mediated by the HDAC4/Gadd45α axis.

The Curcumin Analog CH-5 Exerts Anticancer Effects in Human Osteosarcoma Cells via Modulation of Transcription Factors p53/Sp1.

Curcumin is a potential anticancer drug with poor bioavailability, which limits its clinical use as a therapeutic agent. The aim of this study was a preliminary evaluation of the curcumin analogue CH-5 as a cytotoxic agent in human osteosarcoma cell lines U2OS, MG-63, and Saos-2. CH-5 inhibited cell viability at lower concentrations than curcumin, leading to the induction of apoptosis. The cellular levels of the transcription factors p53 and Sp1 affect the expression of cellular pathways that lead to apoptosis. CH-5 increased p53 protein levels in U2OS cells and reduced Sp1 levels, with a consequent effect on the expression of their target genes DNA methyltransferase 1 (DNMT1) and growth arrest and DNA damage-inducible 45 alpha gene (Gadd45a). CH-5 repressed DNMT1 and increased Gadd45a mRNA expression, which was dependent on p53, as this effect was only observed in the colorectal cancer cell line HCT116 with active p53, but not in the isogenic p53-deficient HCT116 cells. CH-5 also reduced the protein levels of DNMT1, which led to the upregulation of Gadd45a. These results suggest that CH-5 has potentially higher anticancer activity than curcumin, which is associated with the expression of apoptosis-associated genes regulated by the transcription factors Sp1 and p53. Future work on CH-5 will define the therapeutic potential of this compound in vivo.

Multiple DNA damage-dependent and DNA damage-independent stress responses define the outcome of ATR/Chk1 targeting in medulloblastoma cells

Targeting of oncogene-driven replicative stress as therapeutic option for high-risk medullobastoma was assessed using a panel of medulloblastoma cells differing in their c-Myc expression [i.e. group SHH (c-Myc low) vs. group 3 (c-Myc high)]. High c-Myc levels were associated with hypersensitivity to pharmacological Chk1 and ATR inhibition but not to CDK inhibition nor to conventional (genotoxic) anticancer therapeutics. The enhanced sensitivity of group 3 medulloblastoma cells to Chk1 inhibitors likely results from enhanced damage to intracellular organelles, elevated replicative stress and DNA damage and activation of apoptosis/necrosis. Furthermore, Chk1 inhibition differentially affected c-Myc expression and functions. In c-Myc high cells, Chk1 blockage decreased c-Myc and p-GSK3α protein and increased p21 and GADD45A mRNA expression. By contrast, c-Myc low cells revealed increased p-GSK3β protein and CHOP and DUSP1 mRNA levels. Inhibition of Chk1 sensitized medulloblastoma cells to additional replication stress evoked by cisplatin independent of c-Myc. Importantly, Chk1 inhibition only caused minor toxicity in primary rat neurons in vitro. Collectively, targeting of ATR/Chk1 effectively triggers death in high-risk medulloblastoma, potentiates the anticancer efficacy of cisplatin and is well tolerated in non-cancerous neuronal cells.

Sodium Fluoride Arrests Renal G2/M Phase Cell-Cycle Progression by Activating ATM-Chk2-P53/Cdc25C Signaling Pathway in Mice

Background/Aims: Excessive fluoride intake can induce cytotoxicity, DNA damage and cell-cycle changes in many tissues and organs, including the kidney. However, the underlying molecular mechanisms of fluoride-induced renal cell-cycle changes are not well understood at present. In this study, we used a mouse model to investigate how sodium fluoride (NaF) induces cell-cycle changes in renal cells. Methods: Two hundred forty ICR mice were randomly assigned to four equal groups for intragastric administration of NaF (0, 12, 24 and 48 mg/kg body weight/day) for 42 days. Kidneys were taken to measure changes of the cell-cycle at 21 and 42 days of the experiment, using flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR) and western blot methods. Results: NaF, at more than 12 mg/kg body weight, induced G2/M phase cell-cycle arrest in the renal cells, which was supported by the finding of significantly increased percentages of renal cells in the G2/M phase. We found also that G2/M phase cell-cycle arrest was accompanied by up-regulation of p-ATM, p-Chk2, p-p53, p-Cdc25C, p-CDK1, p21, and Gadd45a protein expression levels; up-regulation of ATM, Chk2, p53, p21, and Gadd45a mRNA expression levels; down-regulation of CyclinB1, mdm2, PCNA protein expression levels; and down-regulation of CyclinB1, CDK1, Cdc25C, mdm2, and PCNA mRNA expression levels. Conclusion: In this mouse model, NaF, at more than 12 mg/ kg, induced G2/M phase cell-cycle arrest by activating the ATM-Chk2-p53/Cdc25C signaling pathway, which inhibits the proliferation of renal cells and development of the kidney. Activation of the ATM-Chk2-p53/Cdc25C signaling pathway is the mechanism of NaF-induced renal G2/M phase cell-cycle arrest in this model.

Growth arrest and DNA damage-inducible 45α protects against nonalcoholic steatohepatitis induced by methionine- and choline-deficient diet

Growth arrest and DNA damage-inducible 45 α (Gadd45α) is a stress-inducible protein that plays an important role in cell survival/death and DNA repair, but its contribution to the development of nonalcoholic steatohepatitis (NASH) has not been investigated. C57BL/6 Gadd45a-null and wild-type (WT) mice were treated with a methionine and choline-deficient diet (MCD) for eight weeks and phenotypic changes examined. Gadd45a-null mice had more severe hepatic inflammation and fibrosis, higher levels of mRNAs encoding pro-inflammatory, pro-fibrotic, and pro-apoptotic proteins, and greater oxidative and endoplasmic reticulum (ER) stress compared with WT mice. Indeed, Gadd45a mRNA was induced in response to ER stress in primary hepatocytes. Lipidomic analysis of NASH livers demonstrated decreased triacylglycerol (TG) in MCD-treated Gadd45a-null mice, which was associated with increased mRNAs encoding phospholipase D (Pld1/2), phosphatidic acid phosphatase type 2A, and choline/ethanolamine phosphotransferase 1 (Cept1), involved in the phosphatidylcholine-phosphatidic acid-diacylglycerol cycle, and decreased mRNAs encoding fatty acid (FA)-binding protein 1 (Fabp1) and FA transport protein 5. Treatment of cultured primary hepatocytes with tumor necrosis factor α, transforming growth factor β, and hydrogen peroxide led to the corresponding induction of Fabp1, Pld1/2, and Cept1 mRNAs. Collectively, Gadd45α plays protective roles against MCD-induced NASH likely due to attenuating cellular stress and ensuing inflammatory signaling. These results also suggest an interconnection between hepatocyte injury, inflammation and disrupted glycerophospholipid/FA metabolism that yields a possible mechanism for decreased TG accumulation with NASH progression (i.e., “burned-out” NASH).

Reactive oxygen species mediated NF-κB/p38 feedback loop implicated in proliferation inhibition of HFLS-RA cells induced by 1,7-dihydroxy-3,4-dimethoxyxanthone

1,7-Dihydroxy-3,4-dimethoxyxanthone (XAN) is a bioactive compound isolated from Securidaca inappendiculata Hassk. and exerts the inhibitory effects on fibroblast-like synoviocytes by targeting NF-κB and p38. This study was designed to elucidate mechanisms underlying the divergent regulation on the two pathways in HFLS-RA cells by XAN. Expressions of hallmark proteins and transcription of GADD45α mRNA were determined by Western-blot and RT-qPCR methods, respectively. Fluorescence staining was employed to evaluate intracellular oxidative stress. Effects of XAN and N-acetyl-l-cysteine (NAC) on the proliferation of cells were investigated by MTT assay, and pro-apoptotic effects of XAN were assessed by Annexin V-FITC/PI method. It was found XAN blocked NF-κB signaling in HFLS-RA cells shortly after treatment. Moreover, it up-regulated both transcription and expression of GADD45α, and subsequently activated p38 pathway. As time went on, XAN significantly promoted the generation of reactive oxygen species (ROS), which accompanied with sustained up-regulation of p-p38 and increased apoptosis. 48H later, dual-effects of XAN on NF-κB and p38 were reversed. As activation of p38 and increased apoptosis induced by XAN were antagonized by NAC, they were deemed as ROS mediated effects. Furthermore, the accumulated ROS should also account for the activation of NF-κB in the late stage of treatments via interfering in p38/MSK1/NF-κB feedback. Altogether, these findings suggested XAN-induced ROS contributed great importance to the proliferation inhibition of HFLS-RA cells by mediating NF-κB/p38 feedback loop and apoptosis, which provided us a panoramic view of potential target in the therapy of RA by XAN.

Effects of extremely low frequency electromagnetic field and cisplatin on mRNA levels of some DNA repair genes

AimsIt has been shown that exposure to extremely-low frequency (˂300Hz) oscillating electromagnetic field (EMF) can affect gene expression. The effects of different exposure patterns of 50-Hz EMF and co-treatment of EMF plus cisplatin (CDDP) on mRNA levels of seven genes involved in DNA repair pathways (GADD45A, XRCC1, XRCC4, Ku70, Ku80, DNA-PKcs and LIG4) were evaluated. Main methodsTwo 50-Hz EMF intensities (0.25 and 0.50mT), three exposure patterns (5min field-on/5min field-off, 15min field-on/15min field-off, 30min field-on continuously) and two cell lines (MCF-7 and SH-SY5Y) were used. The mRNA levels were measured using quantitative real-time PCR. Key findingsThe examined genes had tendency to be down-regulated in MCF-7 cells treated with EMF. In the pattern of 15min field-on/15min field-off of the 0.50mT EMF, no increase in mRNA levels were observed, but the mRNA levels of GADD45A, XRCC1, XRCC4, Ku80, Ku70, and LIG4 were down-regulated. A significant elevation in IC50 of CDDP was observed when MCF-7 and SH-SY5Y cells were co-treated with CDDP+EMF in comparison with the cells treated with CDDP alone. GADD45A mRNA levels in MCF-7 and SH-SY5Y cells co-treated with CDDP+EMF were increased and at the same time the mRNA levels of XRCC4, Ku80, Ku70 and DNA-PKcs were down-regulated. SignificancePresent study provides evidence that co-treatment of CDDP+EMF can enhance down-regulation of the genes involved in non-homologous end-joining pathway. It might be suggested that co-treatment of CDDP+EMF could be more promising for sensitizing cancer cells to DNA double strand breaks.

FOXO1 delays skeletal muscle regeneration and suppresses myoblast proliferation.

Unloading stress, such as bed rest, inhibits the regenerative potential of skeletal muscles; however, the underlying mechanisms remain largely unknown. FOXO1 expression, which induces the upregulated expression of the cell cycle inhibitors p57 and Gadd45α, is known to be increased in the skeletal muscle under unloading conditions. However, there is no report addressing FOXO1-induced inhibition of myoblast proliferation. Therefore, we induced muscle injury by cardiotoxin in transgenic mice overexpressing FOXO1 in the skeletal muscle (FOXO1-Tg mice) and observed regeneration delay in skeletal muscle mass and cross-sectional area in FOXO1-Tg mice. Increased p57 and Gadd45α mRNA levels, and decreased proliferation capacity were observed in C2C12 myoblasts expressing a tamoxifen-inducible active form of FOXO1. These results suggest that decreased proliferation capacity of myoblasts by FOXO1 disrupts skeletal muscle regeneration under FOXO1-increased conditions, such as unloading.

Activation of ubiquitin‐proteasome system components in heat‐stressed pig skeletal muscle

Hyperthermia causes metabolic changes and leads to lower lean tissue accretion and increased adipose tissue deposition in animals. The direct effect of heat stress on muscle breakdown has been reported in poultry, rabbits and lactating cows. Muscle breakdown occurs by activating the ubiquitin‐proteasome system and the autophagy‐lysosome pathways. To study the mechanism by which heat stress induces muscle breakdown, the ubiquitin‐protease system in the pig skeletal muscle was examined. Pigs (35 ± 0.8 kg) were assigned to one of three treatments: thermal neutral fed ad libitum (TN, 21°C, n=8), heat stress fed ad libitum (HS, 35°C, n=8), or thermal neutral, pair‐fed to HS intake (PF, n=8) for 7 days. Longissimus dorsi muscle was biopsied on day 3 and 7 relative to start of treatments for real‐time PCR and immunoblotting assays. Heat stress increased activating transcription factor‐4 (ATF4), a stress‐response transcription factor, mRNA abundance by more than 1.5 fold regardless of days (P < 0.05). Heat stress increased growth arrest and DNA damage‐inducible 45a (Gadd45a) mRNA abundance by about 1.5 fold compared with PF muscle (P < 0.05). Similarly, the protein abundance of skeletal muscle Gadd45a was elevated in HS pigs by 50% as well as in PF pigs compared with TN pigs (P < 0.05). The phosphorylation of GSK3 β was similar between groups on day 3 and not different in HS versus PF and TN muscle. However, PF pigs had significantly higher phosphorylated GSK3β compared with TN pigs (P < 0.05). HS pigs exhibited intermediate atrogin‐1 mRNA abundance, which was not different from either TN or PF pigs. However, HS pigs had a significantly higher muscle ring finger‐1 (MuRF1) mRNA abundance (approximately 2 fold) compared with PF pigs (P < 0.05). In conclusion, heat stress activated components of muscle breakdown by inducing AFT4, which increased Gadd45a expression, and subsequent apparent activation of the ubiquitin‐protease system.Support or Funding InformationResults described herein were supported by Agriculture and Food Research Initiative Competitive Grant nos. 2011‐6700330007 and 2014‐67015‐21627 from the USDA National Institute of Food and Agriculture.

Abstract B10: Overexpression of the lncRNA PVT1 contributes to the cervical cancer phenotype, possibly via association with nucleolin

Abstract The plasmacytoma variant translocation 1 gene (PVT1) is an lncRNA that has been designated as an oncogene due to its contribution to the phenotype of multiple cancers. Although the mechanism by which PVT1 influences disease processes has been studied in multiple cancer types, its role in cervical tumorigenesis remains unknown. Thus, the present study was designed to investigate the role of PVT1 in cervical cancer in vitro and in vivo. PVT1 expression was measured by quantitative PCR (qPCR) in 121 invasive cervical carcinoma (ICC) samples, 19 normal cervix samples, and a cervical cell line (SiHa). Further, we used targeted knockdown in conjunction with functional assays to examine PVT1's effects on cervical cancer cell proliferation, migration and invasion, apoptosis, and cisplatin resistance. Our results demonstrate that PVT1 expression is significantly increased in ICC tissue versus normal cervix. PVT1 knockdown in cervical cancer cell lines resulted in significantly decreased cell proliferation, migration and invasion. Further, apoptosis and cisplatin cytotoxicity were significantly increased in PVT1 siRNA-transfected cells. Finally, we show that PVT1 associates with Nucleolin protein and may aid in its stabilization of GADD45A mRNA providing a possible mechanism by which PVT1 overexpression drives cervical carcinogenesis. Citation Format: Marissa Iden, Samantha Fye, Keguo Li, Tamjid Chowdhury, Ramani Ramchandran, Janet S. Rader. Overexpression of the lncRNA PVT1 contributes to the cervical cancer phenotype, possibly via association with nucleolin. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B10.

Growth Differentiation Factor-15 (GDF-15) is a potential marker of radiation response and radiation sensitivity

We have investigated the importance of GDF-15 (secreted cytokine belonging to the TGF-β superfamily) in low and high dose radiation-induced cellular responses. A telomerase immortalized human fibroblast cell line (F11hT) was used in the experiments. A lentiviral system encoding small hairpin RNAs (shRNA) was used to establish GDF-15 silenced cells. Secreted GDF-15 levels were measured in culture medium by ELISA. Cell cycle analysis was performed by flow cytometry. The experiments demonstrated that in irradiated human fibroblasts GDF-15 expression increased with dose starting from 100mGy. Elevated GDF-15 expression was not detected in bystander cells. The potential role of GDF-15 in radiation response was investigated by silencing GDF-15 in immortalized human fibroblasts with five different shRNA encoded in lentiviral vectors. Cell lines with considerably reduced GDF-15 levels presented increased radiation sensitivity, while a cell line with elevated GDF-15 was more radiation resistant than wild type cells. We have investigated how the reduced GDF-15 levels alter the response of several known radiation inducible genes. In F11hT-shGDF-15 cells the basal expression level of CDKN1A was unaltered relative to F11hT cells, while GADD45A and TGF-β1 mRNA levels were slightly higher, and TP53INP1 was considerably reduced. The radiation-induced expression of TP53INP1 was lower in the silenced than in wild type fibroblast cells. Cell cycle analysis indicated that radiation-induced early G2/M arrest was abrogated in GDF-15 silenced cells. Moreover, radiation-induced bystander effect was less pronounced in GDF-15 silenced fibroblasts. In conclusion, the results suggest that GDF-15 works as a radiation inducible radiation resistance increasing factor in normal human fibroblast cells, acts by regulating the radiation-induced transcription of several genes and might serve as a radiation-induced early biomarker in exposed cells.

Hypermethylation of glucocorticoid receptor gene promoter results in glucocorticoid receptor gene low expression in peripheral blood mononuclear cells of patients with systemic lupus erythematosus.

Our aim was to investigate the relationship between the DNA methylation status of glucocorticoid receptor (GR) gene promoter and mRNA expression level of GRα gene of peripheral blood mononuclear cells (PBMCs) in patients with systemic lupus erythematosus (SLE). Fifteen newly emerging SLE patients and fifteen healthy controls were enrolled in this study. DNA and total RNA were extracted from the PBMCs of the SLE patients and healthy controls. The DNA methylation status of GR gene promoter 1 of PBMCs was detected through bisulfite-sequencing PCR. The mRNA expression of GRα, DNA methyltransferases (DNMT1, DNMT3a, DNMT3b) and growth arrest, and DNA damage-induced 45α (GADD45α) of PBMCs was detected using the quantitative real-time polymerase chain reaction method. The mRNA expression of GRα was significantly declined in SLE patients, and the mRNA expression of DNMT1 and GADD45α was significantly elevated in SLE patients. The global methylation status of PBMCs in SLE patients was obviously lower than healthy controls. There were 38, 25, 30, and 49 CpG islands in amplified fragment of GR promoter 1D, 1E, 1F, and 1H, respectively. The overall mean methylation status of the 152 CpG islands of the four promoters was significantly elevated in SLE patients. There was a negative correlation between hypermethylation of GR promoter and GRα mRNA expression in SLE patients. This study demonstrated that hypermethylation of GRα promoter may result in GRα gene low expression in PBMCs of patients with SLE. This study also found that the global methylation status of PBMCs in SLE patients was obviously lower than healthy controls, and it was related to the elevated GADD45α mRNA expression in SLE patients. These conclusions have to be certified by larger-scale clinical studies.