Long non-coding RNA MEG3 inhibits cell growth of gliomas by targeting miR-93 and inactivating PI3K/AKT pathway

Role of long noncoding RNAs in the regulation of alternative splicing in glioblastoma

Glioblastoma multiforme (GBM) is a highly severe primary brain tumor. Despite extensive research, effective treatments remain elusive. Long noncoding RNAs (lncRNAs) play a significant role in both cancer and normal biology. They influence alternative splicing (AS), which is crucial in cancer. Advances in lncRNA-specific microarrays and next-generation sequencing have enhanced understanding of AS. Abnormal AS contributes to cancer invasion, metastasis, apoptosis, therapeutic resistance, and tumor development, including glioma. lncRNA-mediated AS affects several cellular signaling pathways, promoting or suppressing cancer malignancy. This review discusses the lncRNAs regulating AS in glioblastoma and their mechanisms.

Expression of lncRNAs in glioma: A lighthouse for patients with glioma

Glioma is the most common malignant tumour in the central nervous system, accounting for approximately 30 % of the primary tumours of this system. The World Health Organization grades for glioma include: Grade I (pilocytic astrocytoma), Grade II (astrocytoma, oligodastoma, etc.), Grade III (anaplastic astrocytoma, anaplastic oligodastoma, etc.) and Grade IV (glioblastoma). With grade increases, the proliferation, invasion and other malignant biological properties of the glioma are enhanced, and the treatment results are less satisfactory. The overall survival of patients with glioblastoma is less than 15 months. Recent research has focused on the roles of long non-coding RNAs, previously regarded as "transcriptional noise", in diseases, leading to a new understanding of these roles. Therefore, we conducted this review to explore the progress of research regarding the expression and mechanism of long non-coding RNAs in glioma.

Novel sights on therapeutic, prognostic, and diagnostics aspects of non-coding RNAs in glioblastoma multiforme

Glioblastoma Multiforme (GBM) is the primary brain tumor and accounts for 200,000 deaths each year worldwide. The standard therapy includes surgical resection followed by temozolomide (TMZ)-based chemotherapy and radiotherapy. The survival period of GBM patients is only 12-15 months. Therefore, novel treatment modalities for GBM treatment are urgently needed. Mounting evidence reveals that non-coding RNAs (ncRNAs) were involved in regulating gene expression, the pathophysiology of GBM, and enhancing therapeutic outcomes. The combinatory use of ncRNAs, chemotherapeutic drugs, and tumor suppressor gene expression induction might provide an innovative, alternative therapeutic approach for managing GBM. Studies have highlighted the role of Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) in prognosis and diagnosis. Dysregulation of ncRNAs is observed in virtually all tumor types, including GBMs. Studies have also indicated the blood-brain barrier (BBB) as a crucial factor that hinders chemotherapy. Although several nanoparticle-mediated drug deliveries were degrading effectively against GBM in vitro conditions. However, the potential to cross the BBB and optimum delivery of oligonucleotide RNA into GBM cells in the brain is currently under intense clinical trials. Despite several advances in molecular pathogenesis, GBM remains resistant to chemo and radiotherapy. Targeted therapies have less clinical benefit due to high genetic heterogeneity and activation of alternative pathways. Thus, identifying GBM-specific prognostic pathways, essential genes, and genomic aberrations provide several potential benefits as subtypes of GBM. Also, these approaches will provide insights into new strategies to overcome the heterogenous nature of GBM, which will eventually lead to successful therapeutic interventions toward precision medicine and precision oncology.

MiRNA-93: a novel signature in human disorders and drug resistance

miRNA-93 is a member of the miR-106b-25 family and is encoded by a gene on chromosome 7q22.1. They play a role in the etiology of various diseases, including cancer, Parkinson's disease, hepatic injury, osteoarthritis, acute myocardial infarction, atherosclerosis, rheumatoid arthritis, and chronic kidney disease. Different studies have found that this miRNA has opposing roles in the context of cancer. Recently, miRNA-93 has been downregulated in breast cancer, gastric cancer, colorectal cancer, pancreatic cancer, bladder cancer, cervical cancer, and renal cancer. However, miRNA-93 is up-regulated in a wide variety of malignancies, such as lung, colorectal, glioma, prostate, osteosarcoma, and hepatocellular carcinoma. The aim of the current review is to provide an overview of miRNA-93's function in cancer disorder progression and non-cancer disorders, with a focus on dysregulated signaling pathways. We also give an overview of this miRNA's function as a biomarker of prognosis in cancer and emphasize how it contributes to drug resistance based on in vivo, in vitro, and human studies. Video Abstract.

Oncogenic role of microRNA-19b-3p-mediated SOCS3 in glioma through activation of JAK-STAT pathway

The altered expression of microRNA (miRNA) has been implicated in glioma. Here, the current study aimed to clarify the oncogenic effects of miR-19b-3p on cellular processes of glioma and to elucidate the underlying mechanism associated with SOCS3 and the JAK-STAT signaling pathway. Differentially expressed genes related to glioma were initially identified via microarray analysis. Twenty-five glioma patients were selected for clinical data collection, while additional 12 patients with traumatic brain injuries were selected as controls. Cell senescence was assessed by β-galactosidase staining, proliferation by MTT assay and apoptosis by flow cytometry following gain- and/or loss-of-function of miR-19b-3p or SOCS3. Glioma xenograft mouse model was developed through subcutaneous injection to nude mice to provide evidence in vivo. The glioma patients exhibited overexpressed miR-19b-3p and poorly-expressed SOCS3. SOCS3 was identified as a target gene of miR-19b-3p through dual-luciferase reporter gene assay. miR-19b-3p repressed SOCS3 expression and activated the JAK-STAT signaling pathway. Furthermore, miR-19b-3p inhibition promoted apoptosis and senescence, and suppressed cell proliferation through inactivation of the JAK-STAT signaling pathway and up-regulation of SOCS3. The reported regulatory axis was validated in nude mice as evidenced by suppressed tumor growth. Taken together, this study demonstrates that miR-19b-3p facilitates glioma progression via activation of the JAK-STAT signaling pathway by targeting SOCS3, highlighting a novel therapeutic target for glioma treatment.

The Biological Roles and Molecular Mechanisms of Long Non-Coding RNA MEG3 in the Hallmarks of Cancer

Long non-coding RNAs (lncRNAs) are critical regulators in various biological processes involved in the hallmarks of cancer. Maternally expressed gene 3 (MEG3) is lncRNA that regulates target genes through transcription, translation, post-translational modification, and epigenetic regulation. MEG3 has been known as a tumor suppressor, and its downregulation could be found in various cancers. Furthermore, clinical studies revealed that impaired MEG3 expression is associated with poor prognosis and drug resistance. MEG3 exerts its tumor suppressive effect by suppressing various cancer hallmarks and preventing cells from acquiring cancer-specific characteristics; as it could suppress tumor cells proliferation, invasion, metastasis, and angiogenesis; it also could promote tumor cell death and regulate tumor cell metabolic reprogramming. Hence, MEG3 is a potential prognostic marker, and overexpressing MEG3 might become a potential antitumor therapeutic strategy. Herein, we summarize recent knowledge regarding the role of MEG3 in regulating tumor hallmarks as well as the underlying molecular mechanisms. Furthermore, we also discuss the clinical importance of MEG3, as well as their potential in tumor prognosis and antitumor therapeutic strategies.

Transcriptome and chromatin alterations in social fear indicate association of MEG3 with successful extinction of fear

Social anxiety disorder is characterized by a persistent fear and avoidance of social situations, but available treatment options are rather unspecific. Using an established mouse social fear conditioning (SFC) paradigm, we profiled gene expression and chromatin alterations after the acquisition and extinction of social fear within the septum, a brain region important for social fear and social behaviors. Here, we particularly focused on the successful versus unsuccessful outcome of social fear extinction training, which corresponds to treatment responsive versus resistant patients in the clinics. Validation of coding and non-coding RNAs revealed specific isoforms of the long non-coding RNA (lncRNA) Meg3 regulated, depending on the success of social fear extinction. Moreover, PI3K/AKT was differentially activated with extinction success in SFC-mice. In vivo knockdown of specific Meg3 isoforms increased baseline activity of PI3K/AKT signaling, and mildly delayed social fear extinction. Using ATAC-Seq and CUT&RUN, we found alterations in the chromatin structure of specific genes, which might be direct targets of lncRNA Meg3.

Long noncoding RNA Meg3 sponges miR-708 to inhibit intestinal tumorigenesis via SOCS3-repressed cancer stem cells growth

BACKGROUND

Colorectal cancer (CRC) remains the most common gastrointestinal cancer and a leading cause of cancer deaths worldwide, with most showing pathologies indicating the malignant transformation of early stage intestinal stem cells. The long non-coding RNA Meg3, which functions as a tumor suppressor, has been reported to be abnormal in multiple tumorigenesis events; however, the underlying mechanism by which Meg3 contributes to the malignant proliferation of colonic stem cells remains unclear.

METHODS

We analyzed the expression levels of Meg3, miR-708, and SOCS3 in samples from Apc loss-of-function (Apc^min) mice and patients with CRC, particularly in colonic crypt cells. Apc^min mice and AMO/DSS-induced mice model (in vivo) and organoid culture system (in vitro) were used to explore the effect of the Meg3/miR-708/SOCS3 axis on tumorigenesis in the colon. In vitro, we performed RNApull-down, RNA immunoprecipitation, and luciferase reporter assays using DLD1 and RKO cell lines.

FINDINGS

The Meg3/miR-708/SOCS3 signaling axis plays a critical role in the early stage of CRC development. Our data showed Meg3 levels negatively correlate with miR-708 levels both in clinical samples and in the Apc^min mouse model, which indicated that Meg3 acts as a competitive endogenous RNA (ceRNA) of miR-708. Then, miR-708 served as an oncogene, inducing neoplasia in both Apc^min mice and cultured colonic organoids. Put together, miR-708 appears to promote malignant proliferation of colonic stem cells by targeting SOCS3/STAT3 signaling.

INTERPRETATION

These data revealed that Meg3 sponges miR-708 to inhibit CRC development via SOCS3-mediated repression of the malignant proliferation of colonic stem cells. The Meg3/miR-708/SOCS3 signaling axis provides potential targets for the diagnosis and treatment of CRC, particularly early stage CRC.

LncRNA MEG3 Inhibits the Degradation of the Extracellular Matrix of Chondrocytes in Osteoarthritis via Targeting miR-93/TGFBR2 Axis

BACKGROUND

As a degenerative joint disease, osteoarthritis (OA) is characterized by articular cartilage degradation. Long noncoding RNAs (lncRNAs) act critical roles in the regulation of OA development, including affecting the proliferation, apoptosis, extracellular matrix (ECM) degradation, and inflammatory response of chondrocytes. The current study's aim was to investigate the regulatory function and the underlying molecular mechanism of lncRNA MEG3 in ECM degradation of chondrocytes in OA.

METHODS

In the current study, chondrocytes were induced by interleukin-1β (IL-1β) to simulate OA condition, and further assessed cell viability, lncRNA MEG3 and miR-93 expression levels. Overexpression or knockdown of lncRNA MEG3 in chondrocytes treated with IL-1β were performed to investigate the function of MEG3 in regulating cell proliferation, apoptosis and ECM degradation using EdU assay, flow cytometry, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and Western blot. The interaction between MEG3 and miR-93 was assessed using qRT-PCR. Furthermore, overexpression of miR-93 was performed as recovery experiment to explore the functional mechanism of MEG3.

RESULTS

MEG3 was significantly downregulated in chondrocytes treated with IL-1β, whereas miR-93 was upregulated concomitantly. Overexpression of MEG3 induced the proliferation, suppressed the apoptosis, and relieved the degradation of ECM in IL-1β-induced chondrocytes. By contrast, knockdown of MEG3 suppressed the proliferation, promoted the apoptosis, and aggravated ECM degradation in IL-1β induced chondrocytes. In addition, MEG3 was found to relieve the inhibitive expression of TGFBR2 as a competitive endogenous RNA (ceRNA) of miR-93, and then activated transforming growth factor-β (TGF-β) signaling pathway, regulated chondrocytes ECM degradation in IL-1β induced chondrocytes subsequently.

CONCLUSION

LncRNA MEG3 targeted miR-93/TGFBR2 axis, regulated the proliferation, apoptosis and ECM degradation of chondrocytes in OA.

The emerging role of noncoding RNAs in neuroinflammation: Implications in pathogenesis and therapeutic approaches

Noncoding RNAs (ncRNAs) are important regulators of gene expression in different cell processes. Due to their ability in monitoring neural development genes, these transcripts confer neurons with the potential to exert broad control over the expression of genes for performing neurobiological functions. Although the change of ncRNA expression in different neurodegenerative diseases has been reviewed elsewhere, only recent evidence drove our attention to unravel the involvement of these molecules in neuroinflammation within these devastating disorders. Remarkably, the interactions between ncRNAs and inflammatory pathways are not fully recognized. Therefore, this review has focused on the interplay between diverse inflammatory pathways and the related ncRNAs, including microRNAs, long noncoding RNAs, and competing endogenous RNAs in Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, epilepsy, multiple sclerosis, Huntington's disease, and prion diseases. Providing novel insights in the field of combining biomarkers is a critical step for using them as diagnostic tools and therapeutic targets in clinical settings.

Metastasis associated long noncoding RNAs in glioblastoma: Biomarkers and therapeutic targets

Glioblastoma (GBM) is the most aggressive, malignant, and therapeutically challenging Grade IV tumor of the brain. Although the possibility of distant metastasis is extremely rare, GBM is known to cause intracranial metastasis forming aggressive secondary lesions resulting in a dismal prognosis. Metastasis also plays an important role in tumor dissemination and recurrence making GBM largely incurable. Recent studies have indicated the importance of long noncoding RNAs (lncRNAs) in GBM metastasis. lncRNAs are a class of regulatory noncoding RNAs (>200 nt) that interact with DNA, RNA, and proteins to regulate various biological processes. This is the first comprehensive review summarizing the lncRNAs associated with GBM metastasis and the underlying molecular mechanism involved in migration/invasion. We also highlight the complex network of lncRNA/miRNA/protein that collaborate/compete to regulate metastasis-associated genes. Many of these lncRNAs also show attractive potential as diagnostic/prognostic biomarkers. Finally, we discuss various therapeutic strategies and potential applications of lncRNAs as therapeutic targets for the treatment of GBM.

Gossypol ameliorates the IL-1β-induced apoptosis and inflammation in chondrocytes by suppressing the activation of TLR4/MyD88/NF-κB pathway via downregulating CX43

The effects of anti-inflammatory drug gossypol on osteoarthritis (OA) treatment were discussed in this paper. After identified using toluidine blue and immunofluorescence staining of type II collagen, chondrocytes from OA patients were treated with interleukin-1β (IL-1β), gossypol, and overexpressed connexin43 (CX43). In treated chondrocytes, according to MTT assay and flow cytometry, gossypol increased viability and reduced apoptosis of IL-1β induced chondrocytes. Enzyme linked immunosorbent assay (ELISA) suggested that gossypol downregulated inflammatory tumor necrosis factor (TNF)-α level. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot confirmed that gossypol downregulated CX43, nuclear factor-kappa B (NF-κB) p65, TNF-α, toll like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (MyD88) and interleukin-6 (IL-6) expressions. Besides, overexpressed CX43 reversed the effects of gossypol on viability, apoptosis, and expressions of factors related to TLR4/MyD88/NF-κB pathway of IL-1β-induced chondrocytes. In conclusion, gossypol ameliorates IL-1β-induced apoptosis and inflammation in chondrocytes by suppressing TLR4/MyD88/NF-κB pathway via downregulating CX43.

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.

LncRNAs associated with glioblastoma: From transcriptional noise to novel regulators with a promising role in therapeutics

Glioblastoma multiforme (GBM) is the most widespread and aggressive subtype of glioma in adult patients. Numerous long non-coding RNAs (lncRNAs) are deregulated or differentially expressed in GBM. These lncRNAs possess unique regulatory functions in GBM cells, ranging from high invasion/migration to recurrence. This review outlines the present status of specific involvement of lncRNAs in GBM pathogenesis, with a focus on their association with key molecular and cellular regulatory mechanisms. Also, we highlighted the potential of different novel RNA-based strategies that may be beneficial for therapeutic purposes.

Noncoding RNAs in Glioblastoma: Emerging Biological Concepts and Potential Therapeutic Implications

Simple Summary

Since the completion of the Human Genome Project, noncoding RNAs (ncRNAs) have emerged as an important class of genetic regulators. Several classes of ncRNAs, which include microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and piwi-interacting RNAs (piRNAs), have been shown to play important roles in controlling developmental and disease processes. In this article, we discuss the potential roles of ncRNAs in regulating glioblastoma (GBM) formation and progression as well as potential strategies to exploit the diagnostic and therapeutic potential of ncRNAs in GBM.

Abstract

Noncoding RNAs (ncRNAs) have emerged as a novel class of genomic regulators, ushering in a new era in molecular biology. With the advent of advanced genetic sequencing technology, several different classes of ncRNAs have been uncovered, including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and piwi-interacting RNAs (piRNAs), which have been linked to many important developmental and disease processes and are being pursued as clinical and therapeutic targets. Molecular phenotyping studies of glioblastoma (GBM), the most common and lethal cancer of the adult brain, revealed that several ncRNAs are frequently dysregulated in its pathogenesis. Additionally, ncRNAs regulate many important aspects of glioma biology including tumour cell proliferation, migration, invasion, apoptosis, angiogenesis, and self-renewal. Here, we present an overview of the biogenesis of the different classes of ncRNAs, discuss their biological roles, as well as their relevance to gliomagenesis. We conclude by discussing potential approaches to therapeutically target the ncRNAs in clinic.

MiR-93/HMGB3 regulatory axis exerts tumor suppressive effects in colorectal carcinoma cells

OBJECTIVE

MicroRNA (miR)-93 has been proven to mediate the initiation and progression of colorectal carcinoma (CRC); however, the mechanisms by which miR-93 mediates CRC development need deeper elucidation. The present study is designed to investigate the association between miR-93 and high mobility group box 3 (HMGB3), as well as the functions of miR-93, in CRC.

METHODS

miR-93 expression was quantified by RT-qPCR. CRC cells were transfected or cotransfected with miR-93 mimic, miR-93 inhibitor, pcDNA3.1-HMGB3 and sh-HMGB3, and then the proliferative, migratory and invasive capacities were detected in addition to the apoptotic rate. Western blotting assessed the expression levels of HMGB3, PI3K, p-PI3K, AKT and p-AKT. The interaction between miR-93 and HMGB3 was identified.

RESULTS

In CRC tissues, miR-93 was downregulated and HMGB3 was upregulated. LOVO and SW480 cells transfected with miR-93 mimic exhibited reduced proliferation, invasion and migration as well as increased apoptosis. The ratios of p-PI3K/PI3K and p-AKT/AKT were declined after miR-93 mimic was introduced into the CRC cell lines. miR-93 negatively downregulated HMGB3, and introduction of pcDNA3,1-HMGB3 could counteract, in part, the inhibitory effects of miR-93 on the malignant properties of CRC cells as well as the ratios of p-PI3K/PI3K and p-AKT/AKT.

CONCLUSION

miR-93 targeted HMGB3 to block the activation of the PI3K/AKT pathway and thus enhance CRC cell apoptosis.

Silencing of LncRNA PVT1 inhibits the proliferation, migration and fibrosis of high glucose-induced mouse mesangial cells via targeting microRNA-93-5p

Objective: The present study aimed to investigate the regulatory role of long non-coding RNA plasmacytoma variant translocation 1 (PVT1) on high glucose (HG)-induced mouse mesangial cells (MMCs).

Methods: PVT1 expression in diabetic nephropathy (DN) mice and HG-induced MMCs was detected by qRT-PCR. EdU and Colony formation, Annexin V-PI staining, Muse cell cycle, Scratch, and Transwell assays were performed to detect the cell proliferation, apoptosis, cell cycle, migration, and invasion, respectively. The contents of fibrosis factors in cell-culture supernatants were detected by enzyme-linked immunosorbent assay (ELISA). Western blot was performed to detect the expression of factors involved in apoptosis, cell cycle, migration and invasion, fibrosis, and PI3K/Akt/mTOR pathway. The targeting relation between miR-93-5p and PVT1 was predicted by StarBase3.0 (an online software for analyzing the targeting relationship) and identified by Dual-luciferase reporter (DLR) assay.

Results: PVT1 was overexpressed in DN kidney tissues and HG-induced MMCs. HG-induced MMCs exhibited significantly increased EdU-positive cells, cell colonies, S and G₂/M phase cells, migration and invasion ability, and contents of fibrosis factors, as well as significantly decreased apoptosis rate compared with NG-induced MMCs. HG significantly up-regulated Bcl-2, CyclinD1, CDK4, N-cadherin, vimentin, Col. IV, FN, TGF-β1 and PAI-1, and down-regulated Bax, cleaved caspase-3, cleaved PARP, and E-cadherin in MMCs. Silencing of PVT1 eliminated the effects of HG in MMCs and blocked PI3K/Akt/mTOR pathway. MiR-93-5p was a target of PVT1, which eliminated the effects of PVT1 on HG-induced MMCs.

Conclusions: PVT1 silencing inhibited the proliferation, migration, invasion and fibrosis, promoted the apoptosis, and blocked PI3K/Akt/mTOR pathway in HG-induced MMCs via up-regulating miR-93-5p.

Effects and Molecular Mechanism of Single-Nucleotide Polymorphisms of MEG3 on Porcine Skeletal Muscle Development

Maternally expressed gene 3 (MEG3) is a long non-coding RNA that is a crucial regulator of skeletal muscle development. Some single-nucleotide polymorphism (SNP) mutants in MEG3 had strong associations with meat quality traits. Nevertheless, the function and mechanism of MEG3 mutants on porcine skeletal muscle development have not yet been well-demonstrated. In this study, eight SNPs were identified in MEG3 of fat- and lean-type pig breeds. Four of these SNPs (g.3087C > T, g.3108C > T, g.3398C > T, and g.3971A > C) were significantly associated with meat quality and consisted of the CCCA haplotype for fat-type pigs and the TTCC haplotype for lean-type pigs. Quantitative real-time PCR results showed that the expression of MEG3-TTCC was higher than that of MEG3-CCCA in transcription level (P < 0.01). The stability assay showed that the lncRNA stability of MEG3-TTCC was lower than that of MEG3-CCCA (P < 0.05). Furthermore, the results of qRT-PCR, Western blot, and Cell Counting Kit-8 assays demonstrated that the overexpression of MEG3-TTCC more significantly inhibited the proliferation of porcine skeletal muscle satellite cells (SCs) than that of MEG3-CCCA (P < 0.05). Moreover, the overexpression of MEG3-TTCC more significantly promoted the differentiation of SCs than that of MEG3-CCCA (P < 0.05). The Western blot assay suggested that the overexpression of MEG3-TTCC and MEG3-CCCA inhibited the proliferation of SCs by inhibiting PI3K/AKT and MAPK/ERK1/2 signaling pathways. The overexpression of the two haplotypes also promoted the differentiation of SCs by activating the JAK2/STAT3 signaling pathway in different degrees. These data are valuable for further studies on understanding the crucial role of lncRNAs in skeletal muscle development.

Novel insights into the interaction between long non-coding RNAs and microRNAs in glioma

Glioma is the most common brain tumor of the central nervous system. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been identified to play a vital role in the initiation and progression of glioma, including tumor cell proliferation, survival, apoptosis, invasion, and therapy resistance. New documents emerged, which indicated that the interaction between long non-coding RNAs and miRNAs contributes to the tumorigenesis and pathogenesis of glioma. LncRNAs can act as competing for endogenous RNA (ceRNA), and molecular sponge/deregulator in regulating miRNAs. These interactions stimulate different molecular signaling pathways in glioma, including the lncRNAs/miRNAs/Wnt/β-catenin molecular signaling pathway, the lncRNAs/miRNAs/PI3K/AKT/mTOR molecular signaling pathway, the lncRNAs-miRNAs/MAPK kinase molecular signaling pathway, and the lncRNAs/miRNAs/NF-κB molecular signaling pathway. In this paper, the basic roles and molecular interactions of the lncRNAs and miRNAs pathway glioma were summarized to better understand the pathogenesis and tumorigenesis of glioma.

Genetic Influences in Breast Cancer Drug Resistance

Breast cancer is the most common cancer in adult women aged 20 to 50 years. The therapeutic regimens that are commonly recommended to treat breast cancer are human epidermal growth factor receptor 2 (HER2) targeted therapy, endocrine therapy, and systemic chemotherapy. The selection of pharmacotherapy is based on the characteristics of the tumor and its hormone receptor status, specifically, the presence of HER2, progesterone receptors, and estrogen receptors. Breast cancer pharmacotherapy often gives different results in various populations, which may cause therapeutic failure. Different types of congenital drug resistance in individuals can cause this. Genetic polymorphism is a factor in the occurrence of congenital drug resistance. This review explores the relationship between genetic polymorphisms and resistance to breast cancer therapy. It considers studies published from 2010 to 2020 concerning the relationship of genetic polymorphisms and breast cancer therapy. Several gene polymorphisms are found to be related to longer overall survival, worse relapse-free survival, higher pathological complete response, and increased disease-free survival in breast cancer patients. The presence of these gene polymorphisms can be considered in the treatment of breast cancer in order to shape personalized therapy to yield better results.

[Overexpression of lncRNA MEG3 inhibits proliferation and invasion of glioblastoma U251 cells in vitro by suppressing HIF1α expression]

OBJECTIVE

To investigate the effects of overexpression of long noncoding RNA (lncRNA) MEG3 on the proliferation and invasion of glioblastoma U251 cells by suppressing the expression of hypoxia inducible factor 1α(HIF1α).

METHODS

The expression of lncRNA MEG3 and HIF1α mRNA were examined in human fetal glial cells (HFGCs) and U251 cells using realtime quantitative PCR (qRT-PCR), and the expression of HIF1α protein was detected with Western blotting.U251 cells in normal culture or transfected with pcDNA3.1 vector (NC group) or pcDNA3.1-MEG3 vector via lipofectamine2000 were exposed to hypoxia for 12h, and the expressions of HIF1α mRNA and protein were detected with qRT-PCR and Western blotting, respectively.MTT assay and Transwell assay were employed to examine the influence of MEG3 overexpression on the proliferation and invasion of U251 cells.

RESULTS

The expression of MEG3 was significantly lower and HIF1α mRNA and protein expressions were significantly higher in U251 cells than in HFGCs (P < 0.05).In U251 cells, overexpression of MEG3 significantly decreased the mRNA and protein expressions of HIF1α(P < 0.05).Hypoxic exposure for 12h also resulted in significantly lowered expression of HIF1α protein in U251 cells (P < 0.05).Overexpression of MEG3 obviously suppressed the proliferation and invasiveness of U251 cells (P < 0.05).

CONCLUSIONS

MEG3 overexpression inhibits the proliferation and invasion of U251 cells through suppressing the expression of HIF1α mRNA and protein, suggesting that MEG3 may serve as a potential therapeutic target for glioblastomas.

The emerging role of non-coding RNAs in the regulation of PI3K/AKT pathway in the carcinogenesis process

The PI3K/AKT pathway is an intracellular signaling pathway with an indispensable impact on cell cycle control. This pathway is functionally related with cell proliferation, cell survival, metabolism, and quiescence. The crucial role of this pathway in the development of cancer has offered this pathway as a target of novel anti-cancer treatments. Recent researches have demonstrated the role of microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) in controlling the PI3K/AKT pathway. Some miRNAs such as miR-155-5p, miR-328-3p, miR-125b-5p, miR-126, miR-331-3p and miR-16 inactivate this pathway, while miR-182, miR-106a, miR-193, miR-214, miR-106b, miR-93, miR-21 and miR-103/107 enhance activity of this pathway. Expression levels of PI3K/AKT-associated miRNAs could be used to envisage the survival of cancer patients. Numerous lncRNAs such as GAS5, FER1L4, LINC00628, PICART1, LOC101928316, ADAMTS9-AS2, SLC25A5-AS1, MEG3, AB073614 and SNHG6 interplay with this pathway. Identification of the impact of miRNAs and lncRNAs in the control of the activity of PI3K/AKT pathway would enhance the efficacy of targeted therapies against this pathway. Moreover, each of the mentioned miRNAs and lncRNAs could be used as a putative therapeutic candidate for the interfering with the carcinogenesis. In the current study, we review the role of miRNAs and lncRNAs in controlling the PI3K/AKT pathway and their contribution to carcinogenesis.

SNHG1 Promotes Malignant Progression of Glioma by Targeting miR-140-5p and Regulating PI3K/AKT Pathway

PURPOSE

To explore the regulatory mechanism of long non-coding RNA small nucleolar RNA host gene 1 (SNHG1) in glioma.

MATERIALS AND METHODS

The expression of SNHG1 and miR-140-5p in glioma tissues and glioma cell lines (LN-18, KNS-81, and KALS-1) was determined, and the effect of the two on cell proliferation, invasion, and PI3K/AKT pathway was analyzed.

RESULTS

SNHG1 was overexpressed in glioma tissues, while miR-140-5p was underexpressed in them, and there was a significant negative correlation between SNHG1 and miR-140-5p. In addition, both down-regulation of SNHG1 and up-regulation of miR-140-5p significantly inhibited the malignant proliferation and invasion of glioma, intensified the apoptosis, and also significantly suppressed the activation of the PI3K/AKT pathway. The dual-luciferase reporter assay, RNA pull-down assay, and RIP determination all confirmed that there was a targeting relationship between SNHG1 and miR-140-5p, and there was no difference between KNS-81 and KALS-1 cells transfected with SNHG1+mimics and si-SNHG1+inhibitor and those in the si-NC group with unrelated sequences in terms of cell malignant progression.

CONCLUSION

SNHG1/miR-140-5p axis and its regulation on PI3K/AKT pathway might be a novel therapeutic direction to curb the malignant progression of glioma.

PIWI-interacting RNAs and PIWI proteins in glioma: molecular pathogenesis and role as biomarkers

Glioma is the most common primary brain tumor, and is a major health problem throughout the world. Today, researchers have discovered many risk factors that are associated with the initiation and progression of gliomas. Studies have shown that PIWI-interacting RNAs (piRNAs) and PIWI proteins are involved in tumorigenesis by epigenetic mechanisms. Hence, it seems that piRNAs and PIWI proteins may be potential prognostic, diagnostic or therapeutic biomarkers in the treatment of glioma. Previous studies have demonstrated a relationship between piRNAs and PIWI proteins and some of the molecular and cellular pathways in glioma. Here, we summarize recent evidence and evaluate the molecular mechanisms by which piRNAs and PIWI proteins are involved in glioma.

Long non-coding RNA MEG3 promotes cataractogenesis by upregulating TP53INP1 expression in age-related cataract

Age-related cataract (ARC) is the leading cause of visual impairment or even blindness among the aged population globally. Long non-coding RNA (LncRNA) has been proven to be the potential regulator of ARC. The latest study reveals that maternally expressed gene 3 (MEG3) promotes the apoptosis and inhibits the proliferation of multiple cancer cells. However, the expression and role of MEG3 in ARC are unclear. In this study, we investigated the effects of MEG3 in ARC and explored the regulatory mechanisms underlying these effects. We observed that MEG3 expression was up-regulated in the age-related cortical cataract (ARCC) lens capsules and positively correlated with the histological degree of ARCC. The pro-apoptosis protein, active caspase-3 and Bax increased in the anterior lens capsules of ARCC tissue, while the anti-apoptotic protein Bcl-2 decreased compared to normal lens. Knockdown of MEG3 increased the viability and inhibited the apoptosis of LECs upon the oxidative stress induced by H₂O₂. MEG3 was localized in both nucleus and cytoplasm in LECs. MEG3 facilitated TP53INP1 expression via acting as miR-223 sponge and promoting P53 expression. Additionally, TP53INP1 knockdown alleviated H₂O₂-induced lens turbidity. In summary, MEG3 promoted ARC progression by up-regulating TP53INP1 expression through suppressing miR-223 and promoting P53 expression, which would provide a novel insight into the pathogenesis of ARC.

Coding of Glioblastoma Progression and Therapy Resistance through Long Noncoding RNAs

Glioblastoma is the most aggressive and lethal primary brain malignancy, with an average patient survival from diagnosis of 14 months. Glioblastoma also usually progresses as a more invasive phenotype after initial treatment. A major step forward in our understanding of the nature of glioblastoma was achieved with large-scale expression analysis. However, due to genomic complexity and heterogeneity, transcriptomics alone is not enough to define the glioblastoma “fingerprint”, so epigenetic mechanisms are being examined, including the noncoding genome. On the basis of their tissue specificity, long noncoding RNAs (lncRNAs) are being explored as new diagnostic and therapeutic targets. In addition, growing evidence indicates that lncRNAs have various roles in resistance to glioblastoma therapies (e.g., MALAT1, H19) and in glioblastoma progression (e.g., CRNDE, HOTAIRM1, ASLNC22381, ASLNC20819). Investigations have also focused on the prognostic value of lncRNAs, as well as the definition of the molecular signatures of glioma, to provide more precise tumor classification. This review discusses the potential that lncRNAs hold for the development of novel diagnostic and, hopefully, therapeutic targets that can contribute to prolonged survival and improved quality of life for patients with glioblastoma.

Flaming the fight against cancer cells: the role of microRNA-93

There have been attempts to develop novel anti-tumor drugs in cancer therapy. Although satisfying results have been observed at a consequence of application of chemotherapeutic agents, the cancer cells are capable of making resistance into these agents. This has forced scientists into genetic manipulation as genetic alterations are responsible for generation of a high number of cancer cells. MicroRNAs (miRs) are endogenous, short non-coding RNAs that affect target genes at the post-transcriptional level. Increasing evidence reveals the potential role of miRs in regulation of biological processes including angiogenesis, metabolism, cell proliferation, cell division, and cell differentiation. Abnormal expression of miRs is associated with development of a number of pathologic events, particularly cancer. MiR-93 plays a significant role in both physiological and pathological mechanisms. At the present review, we show how this miR dually affects the proliferation and invasion of cancer cells. Besides, we elucidate the oncogenesis or oncosuppressor function of miR-93.

Current advances of long non-coding RNAs mediated by wnt signaling in glioma

Glioma is the most common and aggressive brain tumor in the central nervous system (CNS), in which Wnt signaling pathway has been verified to play a pivotal role in regulating the initiation and progression. Currently, numerous studies have indicated that long non-coding RNAs (lncRNAs) have critical functions across biological processes including cell proliferation, colony formation, migration, invasion and apoptosis via Wnt signaling pathway in glioma. This review depicts canonical and non-canonical Wnt/β-catenin signaling pathway properties and relative processing mechanisms in gliomas, and summarizes the function and regulation of lncRNAs mediated by Wnt signaling pathway in the development and progression of glioma. Ultimately, we hope to seek out promising biomarkers and reliable therapeutic targets for glioma.

Long non-coding RNA PART1 promotes intervertebral disc degeneration through regulating the miR‑93/MMP2 pathway in nucleus pulposus cells

The aim of the present study was to investigate the role of the long non‑coding (lnc)RNA PART1 in nucleus pulposus (NP) cells derived from patients with intervertebral disc degeneration (IDD). The level of PART1 in degenerative NP tissues from patients with IDD, bulging and herniated discs was measured by reverse transcription‑quantitative PCR (RT‑qPCR) analysis. NP cells were isolated from patients with IDD and transfected with siPART1, after which time the growth ability of the NP cells was evaluated by Cell Counting Kit‑8 and colony formation assays, and cell apoptosis was measured by flow cytometry. The levels of the cell proliferation marker Ki‑67 and the apoptosis marker cleaved caspase‑3, and the levels of genes related to extracellular matrix (ECM) synthesis and degradation, were also evaluated by western blotting and RT‑qPCR, as appropriate. Bioinformatics methods predicted that miR‑93 was sponged by PART1, and matrix metallopeptidase (MMP)2 was targeted by miR‑93, which was further confirmed by dual‑luciferase reporter assay. The levels of miR‑93 and MMP2 were also measured in NP tissues, and further rescue experiments were performed to confirm the role of the PART1/miR‑93/MMP2 pathway in NP cells. PART1 was found to be upregulated in degenerative NP tissues, and siPART1 caused an increase in cell growth ability and ECM synthesis, whereas it decreased cell apoptosis and ECM degradation in NP cells. miR‑93 was downregulated and MMP2 was upregulated in degenerative NP tissues. Rescue experiments indicated that the effects of miR‑93 inhibitor on NP cells were abolished by siPART1, and the effect of miR‑93 mimic on NP cells was rescued by MMP2 overexpression. Thus, the results of the present study demonstrated that PART1 may regulate NP cell degeneration through the miR‑93/MMP2 pathway. These findings indicate a novel signaling axis in NP cells that may be explored for the treatment of IDD.

Long non-coding RNA MEG3 functions as a competing endogenous RNA of miR-93 to regulate bladder cancer progression via PI3K/AKT/mTOR pathway

BACKGROUND

Maternally expressed gene 3 (MEG3) is a long non-coding RNA (lncRNA) and involved in progression of various human tumors. However, its underlying regulatory mechanism in tumorigenesis of bladder cancer (BC) remains unclear. To demonstrate effects of MEG3 on BC cell proliferation and elaborate its regulatory mechanism in BC.

METHODS

Aberrant expressions of MEG3 and miR-93-5p were induced by cell transfection. The mRNA and protein expression were analyzed using qRT-PCR and western blot. Cell proliferation was examined by CCK-8 assay and EdU staining. The targeted regulation effect of MEG3 on miR-93-5p was confirmed by luciferase reporter assay. The number of LC3 punctated cells was detected by immunofluorescence. Xeno-graft mouse model was constructed for in vivo validation.

RESULTS

MEG3 was down-regulated with increased expression of miR-93-5p in BC cells and tissues. Luciferase reporter assay showed that miR-93-5p was a direct target of MEG3 and was negatively regulated by MEG3. MEG3 overexpression inhibited cell proliferation and the expression of proliferation-, apoptosis- and autophagy-related proteins. The activation of PI3K/AKT/mTOR pathway was also suppressed with elevated cell apoptosis. miR-93-5p overexpression counteracted these results. In vivo experiments, we confirmed that miR-93-5p overexpression reversed the MEG3 overexpression-mediated suppression on tumor growth and protein expression.

CONCLUSIONS

lncRNA MEG3 could function as a competing endogenous RNA of miR-93 to regulate the tumorigenesis of BC via PI3K/AKT/mTOR pathway. The present research provided a new perspective to understanding the pathogenic mechanism of BC, and an effective therapeutic target for BC.

LncRNA MEG3 influences the proliferation and apoptosis of psoriasis epidermal cells by targeting miR-21/caspase-8

Background

It was reported that microRNA-21(miR-21) was differentially expressed in the keratinocytes of psoriasis patients, and it may influence the apoptosis and proliferation of cells. The role of lncRNA maternally expressed gene3 (MEG3), a competing endogenous RNAs of miR-21, in the progression of psoriasis remains unclear. We aimed to unfold the influence of MEG3 and miR-21 on the proliferation and apoptosis of psoriasis epidermal cells.

Methods

50μg/L TNF-α was used to treat HaCaTs and NHEKs cells for 24 h, and then different experiments were conducted. qRT-PCR were applied for measuring the mRNA level of MEG3, miR-2, and caspase-8, and the protein expression of caspase-8 was measured with western blotting. Flow cytometry was used for assessing apoptosis. Cell proliferation was detected using MTT and colony formation assays. Dual luciferase reporter assay was applied for confirming the binding site between MEG3 and miR-21, miR-21 and Caspase-8.

Results

A cell model for in vitro studying the role of MEG3 in psoriasis pathophysiology was established using HaCaT and HHEKs. MEG3 was significantly down-regulated in HaCaT, HHEKs, and psoriatic skin samples. MEG3 inhibits proliferation and promotes apoptosis of Activated-HaCaT (Act-HaCaT) and Activated-HHEKs (Act- HHEK) by regulating miR-21, and the binding site between MEG3 and miR-21 was identified. We also found that miR-21 could inhibit the level of caspase-8 and identified the binding site between caspase-8 and miR-21. Some down-stream proteins of caspase-8, Cleaved caspase-8, cytc, and apaf-1 were regulated by miR-21 and MEG3.

Conclusion

MEG3/miR-21 axis may regulate the expression of caspase-8, and further influence the proliferation and apoptosis of psoriasis keratinocyte, Act-HaCaT and Act- HHEK. Therefore, our findings may provide a new thought for the study of pathogenesis and treatment of psoriasis.

Long non‑coding RNA MEG3 suppresses the growth of glioma cells by regulating the miR‑96‑5p/MTSS1 signaling pathway

Glioma is one of the most common types of tumor of the central nervous system with high mobility and mortality. The prognosis of patients with high-grade glioma is poor. Therefore, it is urgent to develop the therapeutic strategies for the treatment of glioma. Long non-coding RNAs (lncRNAs) have been reported as potential inducers or suppressors of numerous types of tumors including glioma. Previous studies have revealed that lncRNA maternally expressed gene 3 (MEG3) is involved in the initiation and progression of cancer; however, the underlying mechanisms remain unclear. In the present study, MEG3 was downregulated in glioma tissue. In addition, downregulation of MEG3 was observed in human glioma cell lines compared with normal astrocyte cells. Furthermore, overexpressed MEG3 inhibited the proliferation, migration and invasion of glioma cells. Additionally, microRNA-96-5p (miR-96-5p) was a promising target of MEG3, and the promoting effects of miR-96-5p on cell growth and metastasis could be reversed by upregulated MEG3. Metastasis suppressor 1 (MTSS1) was predicted as the putative target of miR-96-5p, and its expression was restored by MEG3. In summary, the present data provided novel insight into the roles of MEG3 in glioma, and MEG3/miR-96-5p/MTSS1 signaling could be a promising therapeutic target for the treatment of patients with glioma.

Association of LncRNA MEG3 polymorphisms with efficacy of neoadjuvant chemotherapy in breast cancer

BACKGROUND

Breast cancer is the most common malignancy in women, and neoadjuvant chemotherapy has been recommended to the patients with locally advanced breast cancer as the initial treatments. Long non-coding RNA (lncRNA) MEG3, an identified tumor suppressor, has been implicated in the development of various cancers. However, there is no data to evaluate the effect of MEG3 polymorphisms on neoadjuvant treatment in the breast cancer.

METHODS

Genotyping was performed using Nanodispenser Spectro CHIP chip spotting and Mass ARRAY Compact System. Univariate and multivariate logistic regression analyses were used to analyze the associations between the MEG3 polymorphisms and the pathological complete response (pCR). The disease-free survival (DFS) was estimated by the Kaplan-Meier method, and multivariate Cox proportional hazards models were used to calculate the hazard ratios (HRs) with a 95% confidential interval (CI).

RESULTS

A total of 144 patients with available pretreatment blood species were enrolled in the SHPD002 clinic trial of neoadjuvant chemotherapy for breast cancer. MEG3 rs10132552 were significantly associated with good response (Adjusted OR = 2.79, 95% CI 1.096-7.103, p = 0.031) in dominant model. Median follow-up time was 20 months. In multiple regression analysis, rs10132552 TC + CC (adjusted HR = 0.127, 95% CI 0.22-0.728, p = 0.02) and rs941576 AG + GG (adjusted HR = 0.183, 95% CI 0.041-0.807, p = 0.025) were significantly associated with good DFS. MEG3 rs7158663 (OR = 0.377, 95% CI 0.155-0.917, p = 0.032) were associated with a low risk of hemoglobin decrease in dominant models.

CONCLUSIONS

LncRNA MEG3 polymorphisms were associated with the chemotherapy response and toxicity of paclitaxel and cisplatin. The result indicates that MEG3 polymorphisms can be considered as the predictive and prognostic markers for the breast cancer patients.

TRIAL REGISTRATION

Retrospectively registered (ClinicalTrials. Gov identifier: NCT02221999 ); date of registration: Aug 20th, 2014.

Participation of tumor suppressors long non-coding RNA MEG3, microRNA-377 and PTEN in glioma cell invasion and migration

PURPOSE

Glioma is a common and fatal intracranial tumor. Both miR-377 and lncRNA MEG3 are tumor suppressors. This study was performed to investigate the association between miR-377 and lncRNA MEG3 in glioma cells.

METHODS

U118 and U251 cell lines were incubated in Dulbecco's modified Eagle's medium supplemented with miR-377 mimics, MEG3 siRNA (si-MEG3) and/or MEG3 overexpression plasmids (pc-MEG3) for 48 h. Cell migration, invasion, apoptosis, cell cycle distribution and the expression of E26 tansformation-specific-1 (ETS-1), phosphatase and tensin homologue (PTEN), E-cadherin, N-cadherin and β-catenin were detected.

RESULTS

MiR-377 mimics increased MEG3 expression and decreased the number of migrated and invaded U118 and U251 cells, without influence on apoptosis in both cell lines. Si-MEG3 transfection increased U118 cell migration and invasion and rescued miR-377 mimics-induced inhibitory in cell migration and invasion. Si-MEG3 decreased U118 cell apoptosis and induced G0/G1 cell cycle arrest, and pc-MEG3 increased U251 cell apoptosis via arresting cell cycle at G2/M phage. MiR-377 mimics and si-MEG3 increased the relative expression level of N-cadherin mRNA, and both si-MEG3 and pc-MEG3 increased E-cadherin in glioma cells. MiR-377 mimics increased ETS-1 mRNA in U118 cells, but decreased it in U251 cells. PTEN was increased by miR-377 mimics and si-MEG3 and decreased by pc-MEG3 in glioma cells.

CONCLUSIONS

These results suggested the link interaction of MEG3 with miR-377 and PTEN, but not functioning as the competing endogenous RNA. MiR-377 mimics and MEG3 were tumor suppressors in glioma cells through regulating PTEN expression.

Maternally expressed gene 3 in metabolic programming

Maternally Expressed Gene 3 (MEG3) is a long noncoding RNA (lncRNA) that coordinates a diverse array of cellular processes requiring epigenetic regulation of genes and interactions with key signaling proteins and by acting as a competitive endogenous (ce)RNA. Epigenetic modifications driven by in utero nutrition affect MEG3 expression and its role in the development of multiple metabolic disorders. This review examines how epigenetic modification of MEG3 expression can confer adaptedness to different metabolic environments. To this end, we discuss how nutritional status that leads to an increase of MEG3 expression can protect against cancer and metabolic dysfunctions, while interventions that promote MEG3 downregulation minimize the pleiotropic costs associated with its expression. Lastly, we identify research directions that would further shed light on the role of MEG3 in metabolic regulation and in functional imprinted gene networks. This article is part of a Special Issue entitled: ncRNA in control of gene expression edited by Kotb Abdelmohsen.

Long noncoding RNA MEG3 plays a promoting role in the proliferation, invasion, and angiogenesis of lung adenocarcinoma cells through the AKT pathway

The role of long noncoding RNA maternally expressed gene 3 (MEG3) in lung adenocarcinoma has not been explored entirely. In this study, it was demonstrated that the expression of MEG3 was enhanced in lung adenocarcinoma tissues from TCGA database and some specific cell lines, while the survival analysis showed that patients with higher MEG3 levels had lower survival probabilities, which suggested that MEG3 might serve as a lung adenocarcinoma promoter. In addition, the results suggested that the overexpression of MEG3 could promote the proliferation and invasion of lung adenocarcinoma cells. Furthermore, increased MEG3 expression could result in a notable increase in angiogenesis-related factors as well as in the capillary tube formation of endothelial cells, which indicates that the overexpression of MEG3 could promote the angiogenesis of lung adenocarcinoma. From a mechanistic perspective, the results obtained revealed that the upregulation of MEG3 could stimulate the AKT signaling pathway and consequently lead to the biological behaviors mentioned above. In summary, all the results obtained from this study indicated that MEG3 plays a promoting role in the tumorigenesis and angiogenesis of lung adenocarcinoma, which deserves special attention when considered as a potential therapeutic target for lung adenocarcinoma.

Long noncoding RNA STXBP5-AS1 inhibits cell proliferation, migration, and invasion via preventing the PI3K/AKT against STXBP5 expression in non-small-cell lung carcinoma

Long noncoding RNAs participate in carcinogenesis and tumor progression in non-small-cell lung carcinoma (NSCLC), but the mechanisms underlying NSCLC tumorigenesis remain to be fully elucidated. Here, we reported the functional role and potential mechanism of long noncoding RNA syntaxin-binding protein 5-antisense RNA 1 (STXBP5-AS1) in NSCLC. First, our data revealed that the expression levels of STXBP5-AS1 in 31 NSCLC tissues were lower than in adjacent tissues using quantitative polymerase chain reaction (qPCR) and its expression was significantly associated with tumor metastasis of NSCLC patients. Moreover, CCK-8, scratch wound healing and transwell assay suggested that upregulation of STXBP5-AS1 repressed the proliferation, migration, and invasion in A549, NCI-H292, and NCI-H460 cells. To explore the potential mechanism of STXBP5-AS1 in NSCLC, we first investigated the relationship among STXBP5-AS1, STXBP5, and AKT1 in A549 cells. Results indicated that STXBP5-AS1 was negatively related with STXBP5 and AKT1 at messenger RNA expression level using qPCR. In addition, we observed that STXBP5-AS1 had reverse effects on the protein levels of STXBP5 and phosphorylated AKT1 (p-AKT1) in A549 cells via Western blot assay, despite no significant effects on AKT1. Subsequently, LY294002, as the phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) pathway inhibitor, was used to further confirm the regulatory mechanism of STXBP5-AS1, which showed that knockdown of STXBP5-AS1 could rescue the expression of STXBP5 and p-AKT1 protein expression levels in A549 cells. Taken together, our results suggested that STXBP5-AS1, as a tumor suppressor, inhibits cell proliferation, migration, and invasion by preventing the PI3K/AKT against STXBP5 expression in NSCLC.

MEG3: an Oncogenic Long Non-coding RNA in Different Cancers

Long noncoding RNAs (lncRNAs) have recently considered as central regulators in diverse biological processes and emerged as vital players controlling tumorigenesis. Several lncRNAs can be classified into oncogenes and tumor suppressor genes depending on their function in cancer. A maternally expressed gene 3 (MEG3) gene transcripts a 1.6 kb lncRNA whose act as an antitumor component in different cancer cells, such as breast, liver, glioma, colorectal, cervical, gastric, lung, ovarian and osteosarcoma cancer cells. The present review highlights biological function of MEG3 to repress tumor through regulating the major tumor suppressor genes p53 and Rb, inhibiting angiogenesis-related factor, or controlling miRNAs. On the other hand, previous studies have also suggested that MEG3 mediates epithelial-mesenchymal transition (EMT). However, deregulation of MEG3 is associated with the  development and progression of cancer, suggesting that MEG3 may function as a potential biomarker and therapeutic target for human cancers.

Targeting PI3K in cancer: mechanisms and advances in clinical trials

Phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling is one of the most important intracellular pathways, which can be considered as a master regulator for cancer. Enormous efforts have been dedicated to the development of drugs targeting PI3K signaling, many of which are currently employed in clinical trials evaluation, and it is becoming increasingly clear that PI3K inhibitors are effective in inhibiting tumor progression. PI3K inhibitors are subdivided into dual PI3K/mTOR inhibitors, pan-PI3K inhibitors and isoform-specific inhibitors. In this review, we performed a critical review to summarize the role of the PI3K pathway in tumor development, recent PI3K inhibitors development based on clinical trials, and the mechanisms of resistance to PI3K inhibition.

Modulation of the Proliferation/Apoptosis Balance of Vascular Smooth Muscle Cells in Atherosclerosis by lncRNA-MEG3 via Regulation of miR-26a/Smad1 Axis

The balance between proliferation and apoptosis of vascular smooth muscle cells (VSMCs) plays a critical role in the initiation of atherosclerosis. LncRNA-MEG3 is involved in the pathophysiology of atherosclerosis through regulation of endothelial cell proliferation and migration. Its effect on the dysfunction of VSMCs and the corresponding mechanisms are actively researched. In this study, we observed that downregulated lncRNA-MEG3 expression was inversely correlated with the microRNA-26a level in coronary artery disease tissues. The overexpression of lncRNA-MEG3 could inhibit VSMCs proliferation while facilitating apoptosis. Moreover, alteration in the miR-26a/Smad1 axis could antagonize this effect. Bioinformatic analysis indicated that lncRNA-MEG3 could interact with miR-26a via complementary binding sites. The enforced expression of lncRNA-MEG3 could reduce the level of miR-26a in VSMCs, while the expression of Smad1 increases. Further, the direct binding between lncRNA-MEG3 and miR-26a was confirmed via dual-luciferase reporter assay, which indicated that lnc-MEG3 could sponge miR-26a as a competing endogenous RNA. In summary, we propose that lncRNA-MEG3 modulates the proliferation/apoptosis balance of VSMCs in atherosclerosis by regulating the miR-26a/Smad1 axis.

Repression of long non-coding RNA MEG3 restores nerve growth and alleviates neurological impairment after cerebral ischemia-reperfusion injury in a rat model

OBJECTIVE

This study was performed to investigate effect of long non-coding RNA (lncRNA) MEG3 on nerve growth and neurological impairment in a rat model after cerebral ischemia-reperfusion injury (IRI) through the Wnt/β-catenin signaling pathway.

METHODS

Rat models of middle cerebral artery occlusion (MCAO) were established to stimulate an environment of cerebral IRI. The modeled rats were subjected to negative control (NC), MEG3, si-MEG3, classical Wnt pathway inhibitor DKK1 or classical Wnt pathway activator LiCl to validate the effect of MEG3 on neurological impairment and nerve growth. Neurological deficit scoring, fault-foot test and balance beam test were performed to assess neurological impairment. TTC staining, dry-wet weight method and Evan's blue (EB) staining were employed to determine infarct area, water content of brain tissues and blood-brain barrier (BBB) permeability, respectively. Neuronal apoptosis and necrosis were observed by TUNEL staining and Fluoro-Jade C staining. ELISA was adopted to identify levels of nerve growth factors to identify neurogenesis conditions, including brain derived neurotrophic factor (BDNF), nerve growth factor (NGF) and basic fibroblast growth factor (bFGF). Nissl staining was used to detect the survival of neurons in brain tissues of rats. Western blot analysis was used to detect the expression of key proteins in Wnt/β-catenin signaling pathway in brain tissues.

RESULTS

High expression of MEG3 was identified in rat models of MACAO, the brain tissues of which manifested obvious neurological impairment, increased infarct area, water content, BBB permeability, accelerated neuronal apoptosis and necrosis, increased surviving neurons, upregulated expression of key proteins in Wnt/β-catenin signaling pathway and elevated levels of BDNF, NGF and bFGF. With the treatment of si-MEG3, the MEG3 expression was reduced; whereby, modeled rats showed ameliorated neurological impairment, reduced infarct area, water content, BBB permeability, neuronal apoptosis and necrosis and significantly enhanced neurogenesis. The treatment of MEG3 exhibited an opposite trend. After treatment with DKK1, the effect of si-MEG3 was reversed. After treatment with LiCl, the effect of MEG3 was reversed.

CONCLUSION

Based on the findings of this study, down-regulation of lncRNA MEG3 expression enhanced nerve growth and alleviated neurological impairment of rats after cerebral IRI through the activation of the Wnt/β-catenin signaling pathway.

Advanced glycation end products of bovine serum albumin affect the cell growth of human umbilical vein endothelial cells via modulation of MEG3/miR-93/p21 pathway

Advanced glycation end products of BSA (AGE-BSA) contribute to the pathogenesis of diabetic vascular diseases. However, the roles and underlying mechanisms of AGE-BSA in diabetic vascular diseases remain largely unclear. Long non-coding RNAs (lncRNAs) are widely identified and known as gene regulators. However, the roles of lncRNAs in diabetic vascular disease are still vague. In this study, we sought to investigate the contributions of lncRNAs in human umbilical vein endothelial cells (HUVECs) treated with AGE-BSA. We first demonstrated that AGE-BSA reduced the cell viability and inhibited the cell proliferation of HUVECs. Then, we found that lncRNA MEG3 was up-regulated in HUVECs treated with AGE-BSA. Furthermore, inhibition of MEG3 restored the AGE-BSA-induced repression of cell viability and proliferation. In addition, our results revealed that MEG3 played its role via modulation of miR-93 expression in HUVECs treated with AGE-BSA. Furthermore, we illustrated that miR-93 played its role via regulation of p21 in HUVECs treated with AGE-BSA. Ultimately, our study displayed that AGE-BSA exerted its function via modulation of MEG3/miR-93/p21 pathway in HUVECs. Thus, for the first time, we identified the MEG3/miR-93/p21 axis in HUVECs treated with AGE-BSA, which might be a novel regulatory network in diabetic vascular cells, and possess the potential therapeutic value for diabetes mellitus.

Long noncoding RNA CASC9/miR-519d/STAT3 positive feedback loop facilitate the glioma tumourigenesis

Emerging evidence have illustrated the vital roles of long noncoding RNAs (lncRNAs) in glioma. Nevertheless, the majority of their roles and mechanisms in gliomagenesis are still largely unclear. In this study, we investigate the roles of lncRNA CASC9 on glioma tumourigenesis and authenticate its potential mechanisms. Results manifested that CASC9 was highly expressed in glioma specimens and cells, moreover, the ectopic overexpression was correlated with glioma patients’ clinic. Functional studies found that siRNA‐mediated CASC9 silencing inhibited the proliferative ability, invasion in vitro, and impaired the tumour growth in vivo. Mechanical studies revealed that miR‐519d both targeted the 3′‐UTR of CASC9 and STAT3 mRNA, which was identified by luciferase reporter assay and RNA immunoprecipitation (RIP). Moreover, chromatin immunoprecipitation (ChIP) and luciferase reporter assay revealed that STAT3, an oncogenic transcription factor, could bind with the promoter of CASC9 and activate its transcriptional level. In conclusion, our results concluded that CASC9 promotes STAT3 expression via sponging miR‐519d, in return, STAT3 activate CASC9 transcription, forming a positive feedback loop of CASC9/miR‐519d/STAT3. The novel finding provides a potential therapeutic target for glioma.

Interaction of long-chain non-coding RNAs and important signaling pathways on human cancers (Review)

Long non-coding RNAs (lncRNAs) usually refer to non-coding RNA transcripts >200 nucleotides in length. In terms of the full genomic transcript, the proportion of lncRNAs far exceeds that of coding RNA. Initially, lncRNAs were considered to be the transcriptional noise of genes, but it has since been demonstrated that lncRNAs serve an important role in the regulation of cellular activities through interaction with DNA, RNA and protein. Numerous studies have demonstrated that various intricate signaling pathways are closely related to lncRNAs. Here, we focus on a large number of studies regarding the interaction of lncRNAs with important signaling pathways. It is comprehensively illustrated that lncRNAs regulate key metabolic components and regulatory factors of signaling pathways to affect the biological activities of tumor cells. Evidence suggests that the abnormal expression or mutation of lncRNAs in human tumor cells, and their interaction with signaling pathways, may provide a basis and potential target for the diagnosis and treatment of human cancers.

Long Non-Coding RNAs in Gliomas: From Molecular Pathology to Diagnostic Biomarkers and Therapeutic Targets

Gliomas are the most common malignancies of the central nervous system. Because of tumor localization and the biological behavior of tumor cells, gliomas are characterized by very poor prognosis. Despite significant efforts that have gone into glioma research in recent years, the therapeutic efficacy of available treatment options is still limited, and only a few clinically usable diagnostic biomarkers are available. More and more studies suggest non-coding RNAs to be promising diagnostic biomarkers and therapeutic targets in many cancers, including gliomas. One of the largest groups of these molecules is long non-coding RNAs (lncRNAs). LncRNAs show promising potential because of their unique tissue expression patterns and regulatory functions in cancer cells. Understanding the role of lncRNAs in gliomas may lead to discovery of the novel molecular mechanisms behind glioma biological features. It may also enable development of new solutions to overcome the greatest obstacles in therapy of glioma patients. In this review, we summarize the current knowledge about lncRNAs and their involvement in the molecular pathology of gliomas. A conclusion follows that these RNAs show great potential to serve as powerful diagnostic, prognostic, and predictive biomarkers as well as therapeutic targets.