Maternally Expressed Gene 3 Levels Research Articles

The Genetic Variants of Long Noncoding RNA MEG3 and Its Association to the Clinical Features of Diabetic Retinopathy

Purpose This study aimed to investigate the potential correlation between the single-nucleotide polymorphism (SNP) of maternally expressed gene 3 (MEG3) and the clinical manifestations of diabetic retinopathy (DR). Methods Five loci of MEG3 SNPs including rs4081134 (G/A), rs10144253 (T/C), rs7158663 (G/A), rs3087918 (T/G) and rs11160608 (A/C) were genotyped by TaqMan allelic discrimination in 457 non-DR patients and 280 DR individuals. Results The distribution frequency of MEG3 SNP rs7158663 GA (AOR: 0.683, 95% CI: 0.478-0.975, p = 0.036) and MEG3 SNP rs7158663 GA + AA (AOR: 0.686, 95% CI: 0.487-0.968, p = 0.032) were significantly lower in the DR group. And the MEG3 SNP rs7158663 GA + AA (AOR: 0.610, 95% CI: 0.377-0.985, p = 0.043) demonstrated a significantly lower distribution frequency in the male DR group. Besides, the DR patients with MEG3 SNP rs7158663 GA + AA genotype showed a significantly lower HbA1c level than the DR patients with MEG3 SNP rs7158663 GG genotype (7.29 ± 1.23 versus 7.74 ± 1.49, p = 0.013). Moreover, in the analysis using data from gene expression data series database, a higher MEG3 level was significantly correlated to a lower miR-182 level in the database (p = 0.0114). Conclusions In this study, the distribution frequency of MEG3 SNP rs7158663 GA + AA genotype was lower in DR, while the DR would develop under lower HbA1c level in DM patients with this MEG3 SNP variant.

Abstract LB049: Isoharpontigenin inhibits migration and invasion of lung cancer cells through MEG3/EGFR pathway

Abstract Lung cancer is the second most common cancer in both men and women in the United States. Even though treatments including chemotherapy, targeted therapy, and immunotherapy are available, lung cancer has been the leading cause of cancer deaths. The discovery and evaluation of new alternative medications targeting lung cancer are tremendously important for reducing lung cancer mortality. Phytochemicals are very desirable chemotherapeutic agents because of their greater safety profile. Isorhapontigenin (ISO), one of the oral bioavailable dietary stilbenes, can be found in various natural resources. Our result showed that ISO treatment suppressed the invasion and migration of human lung cancer cell lines A549, H23, and H1299 cells. Long non-coding RNA Maternally Expressed Gene 3 (MEG3), a tumor suppressor, was downregulated or lost in various primary human tumor tissues and cancer cell lines. The low expression of MEG3 is correlated with poor prognosis in non-small cell lung cancer (NSCLC). Our results showed that ISO treatment elevated MEG3 levels in these lung cancer cell lines. One of the major genetic causes of lung cancer is mutations in the epidermal growth factor receptor (EGFR) receptor tyrosine kinase, resulting in activation of EGFR which activates several signaling pathways involved in cell proliferation, drug sensitivity, and angiogenesis. Our results showed that ISO decreased the phosphorylation and protein levels of EGFR in A549 cells. Hypoxia-inducible factor-1α (HIF-1α), a transcription factor, regulates the activation of several genes involved in cell proliferation, angiogenesis, invasion, and metastasis. Our results showed that ISO decreased HIF-1α protein levels. Overexpression of MEG3 reduced p-EGFR and HIF-1α, indicating MEG3 negatively regulated EGFR and HIF-1α. Our data also showed that inhibition of EGFR by its tyrosine inhibitor decreased HIF-1α, suggesting that EGFR positively regulates HIF-1α. In cancer cells, Epithelial-Mesenchymal Transition(EMT) endows cells with increased invasiveness and tumor-initiating capacity, contributing to metastasis and resistance to therapeutics. Slug, one of the EMT transcription factors maintains cell plasticity during carcinogenesis. Our results showed that ISO treatment decreased Slugprotein levels in A549 and H23 cells. Transcription factor SOX2 regulates cancer cell proliferation, EMT, migration, invasion, metastasis, tumor initiation, cancer stem cell formation as well as resistance to apoptosis and therapy. Our results showed that ISO decreased SOX2 expression. Knockdown of MEG3 increased the expressions of Slug and SOX2, indicating that MEG3 negatively regulates Slug and SOX2. In conclusion, ISO elevated MEG3, inhibiting EGFR, HIF-1α, Slug, and SOX2, suppressing the migration and invasion of lung cancer cells. Citation Format: Sophia Shi, Zhuo Zhang, Jingxia Li, Huailu Tu, Max Costa. Isoharpontigenin inhibits migration and invasion of lung cancer cells through MEG3/EGFR pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB049.

LncRNA MEG3 Reduces the Ratio of M2/M1 Macrophages Through the HuR/CCL5 Axis in Hepatocellular Carcinoma.

Tumor-associated macrophages play a crucial role in the development of hepatocellular carcinoma (HCC). Our study aimed to investigate the relationship between long coding RNA (lncRNA) maternally expressed gene 3 (MEG3), RNA-binding protein human antigen R (HuR), and messenger RNA C-C motif chemokine 5 (CCL5) in the modulation of M1 and M2 macrophage polarization in HCC. To induce M1 or M2 polarization, LPS/IFNγ- or IL4/IL13 were used to treat bone marrow derived macrophages (BMDMs). The localization of MEG3 in M1 and M2 macrophages was assessed using fluorescence in situ hybridization assay. Expression levels of MEG3, HuR, CCL5, M1, and M2 markers were measured by RT-qPCR or immunofluorescence staining. Flow cytometry was performed to determine the proportion of F4/80+CD206+ and F4/80+CD68+ cells. RNA pulldown assay was performed to detect the binding of lncRNA MEG3 and HuR. The impacts of HuR on CCL5 stability and activity of CCL5 promoter were evaluated using actinomycin D treatment and luciferase reporter assay. Cell migration, invasiveness, and angiogenesis were assessed using transwell migration and invasion assays and a tube formation assay. A mixture of Huh-7 cells and macrophages were injected into nude mice to explore the effect of MEG3 on tumorigenesis. MEG3 promoted M1-like polarization while dampening M2-like polarization of BMDMs. MEG3 bound to HuR in M1 and M2 macrophages. HuR downregulated CCL5 by inhibiting CCL5 transcription in macrophages. In addition, overexpression of MEG3 suppressed cell metastasis, invasion, and angiogenesis by obstructing macrophage M2 polarization. MEG3 inhibited tumorigenesis in HCC via promotion of M1-like polarization and inhibition of M2-like polarization. Rescue experiments showed that depletion of CCL5 in M2 macrophages reversed MEG3-induced suppressive effect on cell migration, invasion, and tube formation. MEG3 suppresses HCC progression by promoting M1-like while inhibiting M2-like macrophage polarization via binding to HuR and thus upregulating CCL5.

M6A-Induced lncRNA MEG3 Promotes Cerebral Ischemia-Reperfusion Injury Via Modulating Oxidative Stress and Mitochondrial Dysfunction by hnRNPA1/Sirt2 Axis.

Ischemic stroke remains one of the major causes of serious disability and death globally. LncRNA maternally expressed gene 3 (MEG3) is elevated in middle cerebral artery occlusion/reperfusion (MCAO/R) rats and oxygen-glucose deprivation/reperfusion (OGD/R)-treated neurocytes cells. The objective of this study is to investigate the mechanism underlying MEG3-regulated cerebral ischemia/reperfusion (I/R) injury. MCAO/R mouse model and OGD/R-treated HT-22 cell model were established. The cerebral I/R injury was monitored by TTC staining, neurological scoring, H&E and TUNEL assay. The levels of MEG3, hnRNPA1, Sirt2 and other key molecules were detected by qRT-PCR and western blot. Mitochondrial dysfunction was assessed by transmission Electron Microscopy (TEM), JC-1 and MitoTracker staining. Oxidative stress was monitored using commercial kits. Bioinformatics analysis, RIP, RNA pull-down assays and RNA FISH were employed to detect the interactions among MEG3, hnRNPA1 and Sirt2. The m6A modification of MEG3 was assessed by MeRIP-qPCR. MEG3 promoted MCAO/R-induced brain injury by modulating mitochondrial fragmentation and oxidative stress. It also facilitated OGD/R-induced apoptosis, mitochondrial dysfunction and oxidative stress in HT-22 cells. Mechanistically, direct associations between MEG3 and hnRNPA1, as well as between hnRNPA1 and Sirt2, were observed in HT-22 cells. MEG3 regulated Sirt2 expression in a hnRNPA1-dependent manner. Functional studies showed that MEG3/Sirt2 axis contributed to OGD/R-induced mitochondrial dysfunction and oxidative stress in HT-22 cells. Additionally, METTL3 was identified as the m6A transferase responsible for the m6A modification of MEG3. m6A-induced lncRNA MEG3 promoted cerebral I/R injury via modulating oxidative stress and mitochondrial dysfunction by hnRNPA1/Sirt2 axis.

Niraparib restrains prostate cancer cell proliferation and metastasis and tumor growth in mice by regulating the lncRNA MEG3/miR-181-5p/GATA6 pathway.

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi), have gained approval for treating patients with castration-resistant prostate cancer (CRPC). Maternally expressed gene 3 (MEG3), a long non-coding RNA (lncRNA), plays a role in inhibiting tumorigenesis through regulating DNA repair genes. This study aimed to investigate the association between the anti-prostate cancer (PCa) effect of niraparib, a representative PARPi, and MEG3 expression, as well as explore the downstream pathway involved. The levels of MEG3, miR-181-5p, GATA binding protein 6 (GATA6) in clinical samples from PCa patients were accessed by RT-qPCR. PC3 cells were treated with niraparib, and the expression of MEG3, miR-181-5p, GATA6 expression was tested. PC3 cell proliferation, migration, and invasion were tested by CCK-8, wound healing, and Transwell assays, respectively. The bindings between miR-181-5p and MEG3/GATA6 were determined by dual-luciferase reporter gene assay. Furthermore, rescue experiments were conducted to investigate the underlying mechanism of MEG3/miR-181-5p/GATA6 axis in PCa progression. Additionally, mice were injected with PC3 cells transfected with sh-MEG3 and treated with niraparib, and the xenograft tumor growth was observed. MEG3 and GATA6 were upregulated and miR-181-5p was downregulated in PCa patients. Niraparib treatment substantially upregulated MEG3 and GATA6, and downregulated miR-181-5p expression in PCa cells. Niraparib effectively restrained PC3 cell proliferation, migration, and invasion. MiR-181-5p targeted to MEG3, and the inhibitory effects of MEG3 overexpression on PC3 cell proliferation and metastasis were abrogated by miR-181-5p overexpression. Moreover, GATA6 was identified as a target of miR-181-5p, and GATA6 silencing abolished the inhibitory effects of miR-181-5p inhibition on PC3 cell proliferation and metastasis. Besides, MEG3 silencing could abrogate niraparib-mediated tumor growth inhibition in mice. Niraparib restrains prostate cancer cell proliferation and metastasis and tumor growth in mice by regulating the lncRNA MEG3/miR-181-5p/GATA6 pathway.

Urinary Long Non-Coding RNA Levels as Biomarkers of Lupus Nephritis.

Emerging evidence suggests that long non-coding RNA (lncRNA) plays important roles in the regulation of gene expression. We determine the role of using urinary lncRNA as a non-invasive biomarker for lupus nephritis. We studied three cohorts of lupus nephritis patients (31, 78, and 12 patients, respectively) and controls (6, 7, and 24 subjects, respectively). The urinary sediment levels of specific lncRNA targets were studied using real-time quantitative polymerase chain reactions. The severity of proteinuria inversely correlated with urinary maternally expressed gene 3 (MEG3) (r = -0.423, p = 0.018) and ANRIL levels (r = -0.483, p = 0.008). Urinary MEG3 level also inversely correlated with the SLEDAI score (r = -0.383, p = 0.034). Urinary cancer susceptibility candidate 2 (CASC2) levels were significantly different between histological classes of nephritis (p = 0.026) and patients with pure class V nephritis probably had the highest levels, while urinary metastasis-associated lung carcinoma transcript 1 (MALAT1) level significantly correlated with the histological activity index (r = -0.321, p = 0.004). Urinary taurine-upregulated gene 1 (TUG1) level was significantly lower in pure class V lupus nephritis than primary membranous nephropathy (p = 0.003) and minimal change nephropathy (p = 0.04), and urinary TUG1 level correlated with eGFR in class V lupus nephritis (r = 0.706, p = 0.01). We identified certain urinary lncRNA targets that may help the identification of lupus nephritis and predict the histological class of nephritis. Our findings indicate that urinary lncRNA levels may be developed as biomarkers for lupus nephritis.

Scutellarein treats neuroblastoma by regulating the expression of multiple targets

AbstractThe aim of this study is to investigate the effect of scutellarein on the proliferation of neuroblastoma cells and the underlying mechanism. Six cell lines were used with drug intervention. Cell Counting Kit‐8 was used to select the best, namely, SH‐SY5Y, and then its IC50 value was determined. To further investigate the mechanism of scutellarin affecting SH‐SY5Y proliferation, quantitative real‐time polymerase chain reaction (qRT‐PCR) was used to detect the expression levels of 11 factors. Scutellarin administration with 300 μM significantly reduced the number of SH‐SY5Y, especially on the 3rd day of exposure to scutellarin. The IC50 value of scutellarin in SH‐SY5Y cells was determined to be 117.8 μM. But the practical results showed that 300 μM was the optimal concentration of scutellarin. qRT‐PCR further detected upregulated maternally expressed gene 3 (MEG3), oncogene c‐Fos (c‐FOS), and c‐jun and downregulated M2 isoform of pyruvate kinase (PKM2), non‐SMC Condensin I Complex Subunit H (NCAPH), epidermal growth factor receptor (EGFR), transforming growth factor (TGF)‐β1, and TGF‐α, suggesting that scutellarin with 300 μM volume inhibited the survival of SH‐SY5Y by regulating the expression of these 8 factors. Scutellarin could be a novel drug for the treatment of neuroblastoma, and its underlying mechanism may be related to the upregulated levels of MEG3, c‐FOS, and c‐jun and downregulated the expression of PKM2, NCAPH, EGFR, TGF‐β1, and TGF‐α.

MEG3 sponges miRNA-376a and YBX1 to regulate angiogenesis in ovarian cancer endothelial cells

ObjectivesRecent studies have demonstrated maternally expressed gene 3 (MEG3) as a tumor suppressor across multiple malignancies. Meanwhile, the role of MEG3 in ovarian cancer needs further investigation. We aim to study the effects of MEG3 on angiogenesis in ovarian cancer and the underlying mechanisms. MethodsThe transcript levels of MEG3 in ovarian cancer samples from the GEPIA database were analyzed and compared to those in normal samples. The effect of MEG3 on the tube formation ability was quantified in ovarian carcinoma-derived microvascular endothelial cells (ODMECs). Through sequence analysis, we identified miR-376a as a major candidate to bind to MEG3. A MEG3-miR-376a binding site was identified via genetic modulation methods. RAS p21 protein activator 1 (RASA1) was screened as a middle player to bridge the role of miR-376a and angiogenesis. The regulation between miR-376a and RASA1 was confirmed via a dual-luciferase reporter assay. Finally, the competition was explored between Y-box binding protein 1 (YBX1) and miR-376a in binding to MEG3. ResultsMEG3 was significantly downregulated in ODMECs compared with normal ovarian endothelial cells. Overexpression of MEG3 led to reduced tube formation of ODMECs. The MS2 hairpin assay showed that MEG3 acted as a platform to sponge miR-376a. RASA1, a key suppressor of tube formation, was directly targeted by miR-376a. Further, MEG3 suppressed angiogenesis through the miR-376a/RASA1 axis in ODMECs. Finally, YBX1 and miR-376a were competitively bound to MEG3. ConclusionThis study uncovered a novel mechanism that MEG3 sponged miRNA-376a and YBX1 to regulate the expression of RASA1 and exert an effect on the angiogenesis of ovarian cancer.

Photobiomodulation (800 nm Light-Emitting Diode) Treatment Promotes Bone Mesenchymal Stem Cell Proliferation Via Long Noncoding RNA MEG3-MicroRNA-217-5P Pathway.

Background: Patients with osteoporosis (OP) have a high risk of bone fracture. Abnormal bone mesenchymal stem cell (BMSC) differentiation is an essential process of OP development. In recent years, photobiomodulation has been shown to effectively promote BMSC proliferation. However, the mechanism by which photobiomodulation promotes BMSC proliferation is unclear. Long noncoding RNAs (lncRNAs) are essential mediators in multiple biological processes. The lncRNA maternally expressed gene 3 (MEG3) is a novel lncRNA gene and is related to cell proliferation. Studies have indicated that MEG3 serves as a promotor in BMSC proliferation. Objective: To investigate the effects and mechanisms of 800 nm light-emitting diode (LED) photobiomodulation in BMSC proliferation. Materials and methods: The BMSCs collected from mouse tibias and femurs were irradiated by 800 nm LED for 180 sec. CCK-8 assay was used to detect the cell viability. A dual-luciferase reporter assay was used to determine IncRNA MEG3 acted as a miR-217-5p sponge. We used reverse transcription-polymerase chain reaction (RT-PCR) and western blot to detect the mRNA and protein levels of MEG3, miR-217-5p, Notch2, Hes1, Hey2. Results: In the present study, we revealed that photobiomodulation (800 nm LED) could increase the mRNA level of MEG3, and protein levels of Notch2, Hes1, and Hey2. Moreover, we also identified that upregulated MEG3 could act as a miR-217-5p sponge to activate the Notch signaling pathway. Conclusions: The current study revealed the MEG3-related mechanism of photobiomodulation treatment in OP and identified potential gene therapies for OP.

Poor semen parameters are associated with abnormal methylation of imprinted genes in sperm DNA

BackgroundAltered sperm DNA methylation patterns of imprinted genes as well as certain spermatogenesis-related genes has been proposed as a possible mechanism of male subfertility. Some reports suggest that there is an elevated risk of congenital diseases, associated with imprinted genes, in children conceived via intra-cytoplasmic sperm injection, due to the involvement of spermatozoa with aberrant imprinted genes obtained from infertile men.MethodsIn this study, the DNA methylation status of the promoter regions of six imprinted genes, namely potassium voltage-gated channel subfamily Q member 1 (KCNQ1), maternally expressed gene 3 (MEG3), insulin-like growth factor 2 (IGF-2), KCNQ1 overlapping transcript 1 (KCNQ1OT1), mesoderm specific transcript (MEST), and paternally expressed gene 3 (PEG3), were detected by a next generation sequencing-based multiple methylation-specific polymerase chain reaction analysis of sperm samples obtained from 166 men who sought fertility evaluation in our Reproductive Medicine Center. Thereafter, the semen samples were classified into subgroups according to sperm motility and DNA integrity status.ResultsAs compared to the normozoospermic group, the samples of the asthenospermic group exhibited significant hypermethylation in two CpG sites of IGF-2 and significant hypomethylation in one CpG site of KCNQ1 as well as three CpG sites of MEST (P < 0.05). However, we did not observe any significant differences in the overall methylation levels of these six imprinted genes (P > 0.05). Additionally, we found that 111 of 323 CpG sites were hypomethylated in the group with DNA fragmentation index (DFI) ≥ 30% as compared to the group with DFI < 30% (P < 0.05). In this case, there were significant differences in the overall methylation levels of MEG3, IGF-2, MEST, and PEG3 (P < 0.05), but not in that of KCNQ1OT1 and KCNQ1 (P > 0.05). Hence, aberrant methylation patterns of imprinted genes were more prevalent in males with poor sperm quality, especially in those with severe sperm DNA damage.ConclusionIn conclusion, abnormal DNA methylation of some CpG sites of imprinted genes are associated with poor sperm quality, including asthenospermia and severe sperm DNA impairment.

Long noncoding RNA maternally expressed gene 3 improves trophoblast dysfunction and inflammation in preeclampsia through the Wnt/β-Catenin/nod-like receptor pyrin domain-containing 3 axis.

Inadequate trophoblastic infiltration and resulting placental hypoxia and inflammation comprise the core pathological basis of preeclampsia (PE). Maternally expressed gene 3 (MEG3) is known to be involved in the pathogenesis of preeclampsia by inhibiting the migration and invasion of trophoblasts and promoting their apoptosis. Nevertheless, the specific underlying downstream molecular mechanism of MEG3 is less well characterized. In this study, we detected lower expression levels of MEG3 and β-Catenin and higher expression of nod-like receptor pyrin domain-containing 3 (NLRP3) in placental tissues of pregnant women with severe preeclampsia (sPE) than in normal pregnancies. Elevated serum levels of IL-1β and TNF-α were also observed in the sPE group. Then, we established a hypoxia/reoxygenation (H/R) model to mimic preeclampsia. Similar results with sPE group were found in the H/R group compared with the control group. In addition, suppressive trophoblast proliferation, migration and invasion and increases in the apoptotic rate and inflammation were also detected in the H/R group. Notably, overexpressing MEG3 markedly improved trophoblast dysfunction and inflammation caused by H/R. However, the effects of MEG3 on trophoblasts, whether upregulated or downregulated, can be reversed by DKK-1 (Wnt/β-Catenin inhibitor) and MCC950 (NLRP3 inhibitor). The current study revealed that MEG3 regulates trophoblast function and inflammation through the Wnt/β-Catenin/NLRP3 axis and provided new insights into the pathogenesis of preeclampsia.

Long non-coding RNA maternally expressed 3 (MEG3) regulates isoflurane-induced cognitive dysfunction by targeting miR-7-5p

This study aimed to investigate the role and mechanism of long non-coding RNA maternally expressed gene 3 (MEG3) in cognitive dysfunction induced by isoflurane (ISO). Morrier water maze analysis was performed to evaluate the cognitive function of rats. Modified modified neurological severity score (mNSS) scores were assessed for neurological damage. The levels of MEG3 in hippocampal tissues of rats and hippocampal neuron cell lines HT22 were examined by reverse transcription-quantitative polymerase chain reaction (qRT-PCR). Moreover, the cell viability and apoptosis were assessed by the Cell Counting Kit-8 (CCK-8) and flow cytometry assay. Indicators of inflammation and oxidative stress were determined using enzyme-linked immunosorbent assay (ELISA) and commercial assay kits. Relationship between MEG3 and microRNA (miR)-7-5p was verified by the dual-luciferase reporter gene assay. MEG3 was increased in hippocampal tissues and HT22 after ISO treatment (p < 0.05). MEG3 downregulation alleviated the increase in neurological severity score and cognitive dysfunction caused by ISO treatment (p < 0.05). In vitro, MEG3 downregulation alleviates the decrease in cell activity and increased apoptosis induced by ISO. What’s more, MEG3 reduction eliminated activation of neuroinflammation and oxidative stress promoted by ISO treatment in rats and HT22 (p < 0.05). MEG3 was confirmed to specifically bind to miR-7-5p. Inhibition of miR-7-5p eliminated the alleviating effects of MEG3 downregulation on cognitive dysfunction caused by ISO treatment. Decreased MEG3 alleviates cognitive dysfunction caused by ISO by targeting miR-7-5p and play a neuroprotective effect. We present a strategy for MEG3 as a potential target for brain protection during anesthesia.

LncRNA MEG3 up-regulates SIRT6 by ubiquitinating EZH2 and alleviates nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global health threat. Here, we presented the significant role of a novel signaling axis comprising long non-coding RNA maternally expressed gene 3 (MEG3), enhancer of zeste homolog 2 (EZH2), and sirtuin 6 (SIRT6) in controlling lipid accumulation, inflammation, and the progression of NAFLD. Mice fed with high-fat diet (HFD) were established as in vitro and in vivo NAFLD models, respectively. Lipid accumulation was measured by oil red O staining and assays for triglycerides or cholesterol. Inflammation was examined by ELISA for pro-inflammatory cytokines. Gene expressions were examined by RT-qPCR or Western blot. Interactions between key signaling molecules were examined by combining expressional analysis, RNA immunoprecipitation, cycloheximide stability assay, co-immunoprecipitation, and chromatin immunoprecipitation. MEG3 level was reduced in FFA-challenged hepatocytes or liver from HFD-fed mice, and the reduction paralleled the severity of NAFLD in clinic. Overexpressing MEG3 suppressed FFA-induced lipid accumulation or inflammation in hepatocytes. By promoting the ubiquitination and degradation of EZH2, MEG3 upregulated SIRT6, an EZH2 target. SIRT6 essentially mediated the protective effects of MEG3 in hepatocytes. Consistently, overexpressing MEG3 alleviated HFD-induced NAFLD in vivo. By controlling the expressions of genes involved in lipid metabolism and inflammation, the MEG3/EZH2/SIRT6 axis significantly suppressed lipid accumulation and inflammation in vitro, and NAFLD development in vivo. Therefore, boosting MEG3 level may benefit the treatment of NAFLD.

MEG3 LncRNA from Exosomes Released from Cancer-Associated Fibroblasts Enhances Cisplatin Chemoresistance in SCLC via a MiR-15a-5p/CCNE1 Axis.

PurposeLong non-coding RNAs (lncRNAs) may act as oncogenes in small-cell lung cancer (SCLC). Exosomes containing lncRNAs released from cancer-associated fibroblasts (CAF) accelerate tumorigenesis and confer chemoresistance. This study aimed to explore the action mechanism of the CAF-derived lncRNA maternally expressed gene 3 (MEG3) on cisplatin (DDP) chemoresistance and cell processes in SCLC.Materials and MethodsQuantitative real-time PCR was conducted to determine the expression levels of MEG3, miR-15a-5p, and CCNE1. Cell viability and metastasis were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-h-tetrazolium bromide and invasion assays, respectively. A xenograft tumor model was developed to confirm the effect of MEG3 overexpression on SCLC progression in vivo. Relationships between miR-15a-5p and MEG3/CCNE1 were predicted using StarBase software and validated by dual luciferase reporter assay. Western blotting was used to determine protein levels. A co-culture model was established to explore the effects of exosomes on MEG3 expression in SCLC cell lines.ResultsMEG3 was overexpressed in SCLC tissues and cells. MEG3 silencing significantly repressed cell viability and metastasis in SCLC. High expression of MEG3 was observed in CAF-derived conditioned medium (CM) and exosomes, and promoted chemoresistance and cancer progression. Additionally, MEG3 was found to serve as a sponge of miR-15a-5p to mediate CCNE1 expression. Overexpression of miR-15a-5p and knockout of CCNE1 reversed the effects of MEG3 overexpression on cell viability and metastasis.ConclusionMEG3 lncRNA released from CAF-derived exosomes promotes DDP chemoresistance via regulation of a miR-15a-5p/CCNE1 axis. These findings may provide insight into SCLC therapy.

LncRNA MEG3 modulates hepatic stellate cell activation by sponging miR‑145 to regulate PPARγ.

It is important to determine the mechanism of liver fibrosis for targeted therapy and the development of targeted therapies for liver fibrosis may offer promise for patients with liver disease. Long non-coding RNAs (lncRNAs) serve a role in hepatic fibrosis. The lncRNA maternally expressed gene 3 (MEG3) has been confirmed to inhibit liver fibrosis. The present study investigated the role of the MEG3 in healthy patients and patients with liver fibrosis. The expression levels of MEG3 and microRNA (miR)-145 in the serum of healthy volunteers and patients with liver fibrosis and in LX-2 cells were detected using reverse transcription-quantitative PCR. A dual-luciferase reporter assay was used to determine the targeting relationship between MEG3 and miR-145, and the targeting relationship between miR-145 and peroxisome proliferator-activated receptor γ (PPARγ). The protein expression levels of PPARγ, α-smooth muscle actin (α-SMA) and collagen I (COL1A1) were detected using western blotting. The expression levels of α-SMA and COL1A1 were also determined using immunofluorescence. Finally, a Cell Counting Kit-8 assay was performed to assess the proliferative ability of LX-2 cells. A significantly reduced MEG3 expression level was demonstrated in serum from patients with liver fibrosis compared with serum from healthy controls. TGF-β1 induced a significantly decreased MEG3 expression level in LX-2 human hepatic stellate cells in vitro. The TGF-β1-induced increases in cell proliferation and α-SMA and COL1A1 protein expression levels were reversed following MEG3 overexpression. The results also demonstrated that MEG3 sponged miR-145 and competed endogenously with miR-145 to regulate PPARγ. In summary, the present study identified MEG3 as an anti-fibrotic lncRNA and provided new information regarding the role of MEG3 in liver fibrosis. MEG3 may therefore be a potential target in the treatment of liver fibrosis.

Prognostic Value of MEG3 and Its Correlation With Immune Infiltrates in Gliomas.

Accumulating evidence has revealed that dysregulated lncRNA expression contributes to the onset and progression of cancer. However, the mechanistic role of lncRNA in glioma progression and tumor immunology remains largely unknown. This study aimed to evaluate the significance of maternally expressed gene 3 (MEG3) in the prognosis of and its immune-related roles in gliomas. The expression levels of MEG3 were analyzed using Oncomine and TIMER database. As an important imprinted gene, the copy number variation (CNV) of MEG3 in both glioblastoma multiforme (GBM) and low-grade glioma (LGG) were analyzed using GSCALite database, whereas its prognostic significance was assessed using PrognoScan and GEPIA databases. The relationship between MEG3 and tumor-infiltrated immune cells was analyzed using TIMER. Results showed that MEG3 expression was lower in most of the human cancer tissues than in the normal tissues. We also found that heterozygous deletion of MEG3 occurred more frequent than heterozygous amplification in gliomas, and mRNA expression of MEG3 was significantly positively correlated with its CNV in both the GBM and LGG group. Survival analysis showed that the CNV level of MEG3 had significant correlation with overall survival (OS) and progression-free survival (PFS) compared with wild type in LGG. Lower MEG3 expression was related with poor prognosis. Further analysis showed that in GBM, MEG3 expression level was significantly positively correlated with that of infiltrating CD8+ T cells and significantly negatively correlated with that of infiltrating dendritic cells. In LGG, MEG3 expression level was significantly negatively correlated with levels of infiltrating B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells. Univariate Cox survival analysis demonstrated that only the level of infiltrating dendritic cells significantly affected the survival time of patients with GBM, while all six types of immune cells had a significant effect on the survival time of patients with LGG. Furthermore, MEG3 expression showed strong correlations with multiple immune markers in gliomas, especially in LGG. The current findings suggest that MEG3 expression might serve as a possible prognostic marker and potential immunotherapeutic target for gliomas.

LncRNA MEG3 Downregulation Relieves Intracerebral Hemorrhage by Inhibiting Oxidative Stress and Inflammation in an miR-181b-Dependent Manner.

BackgroundThis study was designed to illustrate the effects and latent mechanism of lncRNA maternally expressed gene 3 (MEG3) on intracerebral hemorrhage (ICH)-induced brain injury.Material/MethodsAn ICH rat model was generated to determine the role of lncRNA MEG3 in ICH. The interaction between lncRNA MEG3 and microRNA (miR)-181b were confirmed by Starbase and dual-luciferase reporter assay. One hour (h) or 3 days after ICH stimulation, rat neurological injury was evaluated by modified Neurological Severity Score (mNSS). Brain water content and cell apoptosis were assessed using brain edema assessment and flow cytometry (FCM), respectively. Caspase3 activity was also determined. Enzyme-linked immunosorbent assay (ELISA) was applied to evaluate the levels of pro-inflammatory cytokines. Moreover, the representative biomarkers of oxidative stress were evidenced using detection kits.ResultsThe lncRNA MEG3 level in ICH rat brain tissues was higher than that in the sham group. miR-181b was a direct target of lncRNA MEG3 and it was downregulated in brain tissues of ICH rats. Notably, we found that neurobehavioral scores, brain water content, and neuronal apoptosis were decreased and caspase3 activity was reduced in MEG3-shRNA-treated ICH rats, while we observed the opposite result in ICH+MEG3-shRNA+miR-181b inhibitor rats. Further analyses revealed that MEG3-shRNA inhibited inflammatory cytokines release and reduced oxidative stress. All these results were reversed by miR-181b inhibitor. In addition, MEG3-shRNA activated the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway, which was reversed by miR-181b inhibitor.ConclusionsMEG3-shRNA restrained oxidative stress and inflammation following ICH in an miR-181b-dependent manner.

Long Noncoding RNA Maternally Expressed Gene 3 Targets miR-30b and Regulates the AKT Serine/Threonine Kinase 1/Phosphoinositide 3-Kinase Signaling Pathway of H2O2-Induced Proliferation, Apoptosis, and Oxidative Stress in Retinal Ganglion Cells

Oxidative stress is an important factor affecting retinal ganglion cell (RGC) apoptosis. RGC apoptosis is the main pathophysiological feature of visual impairment as a result of glaucoma. Recently, it has been found that long noncoding RNA (lncRNA) and microRNAs are involved in RGC apoptosis. Here, the function of lncRNA maternally expressed gene 3 (MEG3) and miR-30b in H2 O2-induced RGC proliferation, apoptosis, and oxidative stress was investigated. The expression levels of MEG3 and miR-30b were detected by RT-PCR; the effects of MEG3 and miR-30b on the proliferation and apoptosis of RGCs were observed by flow cytometry; the levels of apoptosis-related proteins and AKT/PI3K signal pathway proteins were detected by protein immunoassay; and the regulation of miR-34a by pvt1 was verified by in vivo and in vitro experiments. The expression of MEG3 and miR-30b increased and decreased significantly in RGCs treated by H2O2. MEG3 expression decreased, apoptosis level-related proteins decreased, the apoptosis rate reduced, and the activity of MDA and SOD decreased. When the expression of miR-34a was inhibited, the proliferation rate of RGCs increased, the apoptosis rate decreased, and the level of apoptosis-related proteins decreased, which reversed MEG3’s effect on RGC apoptosis and proliferation. Furthermore, pvt1 could bind the miR-30b promoter and regulate it with in vitro expression and in vivo expression. Besides, we found that miR-30b can regulate the AKT/PI3K signaling pathway and participate in cell apoptosis and hyperplasia in stress response. LncRNA MEG3 targets miR-30b and regulates the AKT/PI3K signaling pathway on H2 O2-induced cell apoptosis, hyperplasia, and oxidative stress of RGCs.

The expression levels of plasma dimethylglycine (DMG), human maternally expressed gene 3 (MEG3), and Apelin-12 in patients with acute myocardial infarction and their clinical significance.

To analyze the expression levels of plasma dimethylglycine (DMG), human maternally expressed gene 3 (MEG3), and Apelin-12 in patients with acute myocardial infarction (AMI) and explore their clinical significance. One hundred and ten patients with suspected AMI (chest pain duration <6 h) who were admitted to our hospital between December 2018 and June 2020 were included. Plasma DMG, MEG3, and Apelin-12 levels were measured at the time of admission. The levels of plasma DMG, MEG3, and Apelin-12, as well as the general data and admission baseline data of these patients were then compared with those of non-AMI patients. The receiver operating characteristic (ROC) curve was used to analyze the clinical value of plasma DMG, MEG3, and Apelin-12 levels for the early diagnosis of AMI. Among the 110 patients with chest pain suspected of AMI, 34 were clinically diagnosed with AMI, and 76 were non-AMI patients. The proportion of males, smoking, history of myocardial infarction, and congestive heart failure in the AMI group were higher than those of the non-AMI group. The proportions of systolic blood pressure (SBP), ST-segment elevation, and electrocardiogram (ECG) dynamic changes on admission were also higher in the AMI group compared to those of the non-AMI group (P<0.05). The plasma DMG, MEG3, and Apelin-12 levels of patients in the AMI group on admission were higher than those of the non-AMI group (P<0.05); all have diagnostic value for AMI upon admission. The area under the curve (AUC) of MEG3 was higher than that of both DMG and Apelin-12, however the difference was not statistically significant (Z=1.378, 0.934, P=0.168, 0.350). Using 0.015 as the cut-off value for MEG3-messenger ribonucleic acid (mRNA), the sensitivity and specificity for diagnosing AMI were 85.29% and 81.58%, respectively. Our results showed that the plasma levels of DMG, MEG3, and Apelin-12 in patients with AMI were high, and thus, they can be used as biomarkers for the early diagnosis of AMI. Among them, MEG3 was the most effective in early diagnosing AMI.

Implication of LncRNAs MEG3 and LINC00305 in Pathophysiological Mechanisms associated with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a joint destructive disorder with great morbidity. Early diagnosis and early and effective therapy may prevent joint damage and lead to better long-term results. Therefore, reliable biomarkers and outcome measures are needed. Complex interplay between multiple risk factors contributes to RA. These risk factors include environmental factors, genetic factors and epigenetic modifications. Long non-coding RNAs (lncRNAs) are involved in these epigenetic mechanisms. Accumulating evidence has shown that lncRNAs participate in the processes of inflammation, aberrant proliferation, apoptosis and angiogenesis. They also play roles in autoimmune diseases, such as SLE, Sjogren syndrome, RA and multiple sclerosis. Maternally expressed gene 3 (MEG3) is a maternally expressed lncRNA of the imprinted DLK1–MEG3 locus located on human 14q32 chromosome. It functions as a tumor suppressor. Decreased MEG3 expression has been observed in various human cancers, both type 1 and type 2 diabetes, osteoarthritis and in RA. Decreased serum levels of lncRNA MEG3 in RA could be attributed to MEG3 promoter hypermethylation induced by hypoxia. This downregulation was associated with increased inflammation, cell proliferation and cell invasion and decreased apoptosis. Long intergenic non-Protein coding RNA 00305 (LINC00305) was identified as a pro-inflammatory atherosclerosis-associated lncRNA. RA was associated with increased LINC00305 which served as a regulator of inflammatory, hypoxic, invasive, apoptotic and proliferative mechanisms associated with RA.