MEG3 inhibits proliferation and invasion and promotes apoptosis of human osteosarcoma cells

Network analysis reveals a major role for 14q32 cluster miRNAs in determining transcriptional differences between IGHV-mutated and unmutated CLL

Chronic lymphocytic leukaemia (CLL) cells can express unmutated (U-CLL) or mutated (M-CLL) immunoglobulin heavy chain (IGHV) genes with differing clinical behaviours, variable B cell receptor (BCR) signalling capacity and distinct transcriptional profiles. As it remains unclear how these differences reflect the tumour cells' innate pre/post germinal centre origin or their BCR signalling competence, we applied mRNA/miRNA sequencing to 38 CLL cases categorised into three subsets by IGHV mutational status and BCR signalling capacity. We identified 492 mRNAs and 38 miRNAs differentially expressed between U-CLL and M-CLL, but only 9 mRNAs and 0 miRNAs associated with BCR competence within M-CLL. Of the IGHV-associated miRNAs, (14/38 (37%)) derived from chr14q32 clusters where all miRNAs were co-expressed with the MEG3 lncRNA from a cancer associated imprinted locus. Integrative analysis of miRNA/mRNA data revealed pronounced regulatory potential for the 14q32 miRNAs, potentially accounting for up to 25% of the IGHV-related transcriptome signature. GAB1, a positive regulator of BCR signalling, was potentially regulated by five 14q32 miRNAs and we confirmed that two of these (miR-409-3p and miR-411-3p) significantly repressed activity of the GAB1 3'UTR. Our analysis demonstrates a potential key role of the 14q32 miRNA locus in the regulation of CLL-related gene regulation.

A review of current evidence about lncRNA MEG3: A tumor suppressor in multiple cancers

Long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3) is a lncRNA located at the DLK1-MEG3 site of human chromosome 14q32.3. The expression of MEG3 in various tumors is substantially lower than that in normal adjacent tissues, and deletion of MEG3 expression is involved in the occurrence of many tumors. The high expression of MEG3 could inhibit the occurrence and development of tumors through several mechanisms, which has become a research hotspot in recent years. As a member of tumor suppressor lncRNAs, MEG3 is expected to be a new target for tumor diagnosis and treatment. This review discusses the molecular mechanisms of MEG3 in different tumors and future challenges for the diagnosis and treatment of cancers through MEG3.

Possible Role of lncRNA MEG3-microRNA-21 and Endoplasmic Reticulum (ER) Stress Proteins in the Pathogenesis of Psoriasis Vulgaris

BACKGROUND

Psoriasis is a chronic inflammatory immune mediated disease arising from interaction between genetic risk variants and the environment. Maternally expressed gene3 (MEG3) is a long noncoding RNA (lncRNA) known for gene transcription regulation and inhibiting proliferation. MEG3 competes with microRNA (miRNA-21) influencing cell proliferation and apoptosis balance. Endoplasmic reticulum (ER) stress proteins promote cell survival via unfolded protein response (UPR) influenced by MEG3. We aimed to detect the possible role of MEG3, miRNA-21 and ER stress proteins in pathogenesis of psoriasis vulgaris.

METHODS

Human GRP78, ATF6, caspase3 tissue levels were assayed by Enzyme Linked Immunosorbent Assay (ELISA). Assessment of long non-coding MEG3 and miRNA 21 expressions was done by quantitative real time polymerase chain reaction (qRT-PCR).

RESULTS

Expression of MEG3 was significantly downregulated, while miRNA-21 was remarkably upregulated, ER stress proteins GRP78, ATF6, and caspase 3 all showed low levels in homogenized psoriatic lesions when compared to normal skin. miRNA 21 and MEG3 were identified as possible diagnostic markers for psoriasis vulgaris.

DISCUSSION

MEG3 is barely expressed in psoriatic lesions while miRNA-21 expression is remarkably elevated but when correlated to each other there was unexpected positive correlation. MEG3 and miRNA-21 were identified as possible diagnostic markers for psoriasis. Undifferentiated psoriatic lesions have very weak UPR.

Comparison of Selected Non-Coding RNAs and Gene Expression Profiles between Common Osteosarcoma Cell Lines

Simple Summary

Osteosarcoma (OS) is a malignant tumour affecting mainly children and elderly people. Despite significant advances in cancer medicine, osteosarcoma patients’ survival is not improving. The primary treatment methods are established using in vitro models that rely upon the application of well-established cell lines, including U-2 OS, Saos-2 and MG-63. The molecular phenotype of these cell lines is still not fully outlined. Therefore, our study aimed to establish the expression profile of molecular markers related to osteosarcoma survival, progression and metastasis. Non-bone-related cells were used as a reference, i.e. HeLa cell line and human adipose-derived stromal cells (hASCs). Evaluated osteosarcoma cell lines showed characteristic phenotypes with unique patterns related to upregulation of MMP-7, MMP-14, BMP-7, miR-21-5p, miR-124-3p and downregulation of lncRNA MEG3. Our findings may facilitate the selection of the most reliable cellular model for pre-clinical investigations focused on developing new and satisfying methods of osteosarcoma therapy.

Abstract

Osteosarcoma (OS) is a bone tumour affecting adolescents and elderly people. Unfortunately, basic treatment methods are still underdeveloped, which has a high impact on the poor survivability of the patients. Studies designed to understand the underlying mechanisms of osteosarcoma development, as well as preclinical investigations aimed at establishing novel therapeutic strategies, rely significantly upon in vitro models, which apply well-established cell lines such as U-2 OS, Saos-2 and MG-63. In this study, the expression of chosen markers associated with tumour progression, metastasis and survival were identified using RT-qPCR. Levels of several onco-miRs (miR-21-5p, miR-124-3p, miR-223-3p and miR-320a-3p) and long non-coding RNA MEG3 were established. The mRNA expression of bone morphogenetic proteins (BMPs), including BMP-2, BMP-3, BMP-4, BMP-6, BMP-7, as well as their receptors: BMPR-IA, BMPR-IB and BMPR-II was also determined. Other tested markers included metalloproteinases, i.e., MMP-7 and MMP-14 and survivin (BIRC5), C-MYC, as well as CYCLIN D (CCND1). The analysis included comparing obtained profiles with transcript levels established for the osteogenic HeLa cell line and human adipose-derived stromal cells (hASCs). The tested OS cell lines were characterised by a cancer-related phenotype, such as increased expression of mRNA for BMP-7, as well as MMP-7 and MMP-14. Osteosarcoma cells differ considerably in miR-21-5p and miR-124-3p levels, which can be related to uncontrolled tumour growth. The comprehensive examination of osteosarcoma transcriptome profiles may facilitate the selection of appropriate cell models for preclinical investigations aimed at the development of new strategies for OS treatment.

The Impact of Single Nucleotide Polymorphism in the Long Non-coding MEG3 Gene on MicroRNA-182 and MicroRNA-29 Expression Levels in the Development of Breast Cancer in Egyptian Women

Early-stage detection of BC is a critical factor for effective treatment of the disease and can increase the survival rate of BC patients. Long non-coding RNAs can act as miRNA decoys by sequestering miRNAs, thus acting as competing endogenous RNAs and leading to re-expression of miRNA target genes. Maternally expressed 3 (MEG3) is LncRNA and it was reported to be tumor suppressor in breast cancer. The study aims to investigate the effect of MEG3 SNP (rs7158663 G/A) and its association with breast cancer risk in the Egyptian population. In addition, demonstrate the consequence of the MEG3 polymorphism on the expression levels of MEG3, miR-182, and miRNA-29. MEG3 rs7158663 G/A was genotyped and serum MEG3, miRNA-182, and miRNA-29 were measured in 180 breast cancer, 120 FA, and 150 controls by the qPCR. Frequencies of MEG3 rs7158663 GA/AA genotype and A allele were significantly higher in BC patients compared to the controls results showed that serum MEG3 levels were significantly lower, according to the presence of the A allele in different study groups while the expression of miR-182 and miRNA 29 were significantly elevated. MEG3, miR-182, and miRNA-29 are key genes involved in the development of BC, are considered as a novel potential non-invasive diagnostic biomarker for BC.

Long non‑coding RNA PCAT6 promotes the development of osteosarcoma by increasing MDM2 expression

Osteosarcoma is a severe malignant tumor. Several studies indicated that lncRNA prostate cancer-associated transcript 6 (PCAT6) promoted the development of multiple types of cancers. Studies have also revealed that MDM2 could aggravate tumor symptoms inhibiting P53 expression. However, whether lncRNA PCAT6 could affect the proliferation and metastasis of osteosarcoma cells by regulating P53 expression is unclear. The present study established lncRNA PCAT6-overexpressing osteosarcoma cells. Cell Counting Kit-8, wound healing and Transwell assays were performed to detect the change in proliferation, migration and invasion of these cells, respectively. Subsequently, E3 ubiquitin-protein ligase Mdm2 (MDM2), P53 and P21 expression were determined using western blotting. Finally, MDM2 expression was inhibited and the proliferation, migration and invasion of these cells was determined again. The present study found that the proliferation, migration and invasion of osteosarcoma cells increased following overexpression of lncRNA PCAT6. MDM2 expression was upregulated while the levels of P53 and P21 decreased following overexpression of lncRNA PCAT6. However, the proliferation, migration and invasion of osteosarcoma cells were inhibited following MDM2 knockdown. Additionally, P53 and P21 was rescued following MDM2 knockdown. To conclude, lncRNA PCAT6 promoted the proliferation, migration and invasion of osteosarcoma cells by promoting the expression of MDM2 and suppressing the expression of P53 and P21.

Long non-coding RNA MEG3 is involved in osteogenic differentiation and bone diseases (Review)

Osteogenic differentiation originating from mesenchymal stem cells (MSCs) requires tight co-ordination of transcriptional factors, signaling pathways and biomechanical cues. Dysregulation of such reciprocal networks may influence the proliferation and apoptosis of MSCs and osteoblasts, thereby impairing bone metabolism and homeostasis. An increasing number of studies have shown that long non-coding (lnc)RNAs are involved in osteogenic differentiation and thus serve an important role in the initiation, development, and progression of bone diseases such as tumors, osteoarthritis and osteoporosis. It has been reported that the lncRNA, maternally expressed gene 3 (MEG3), regulates osteogenic differentiation of multiple MSCs and also acts as a critical mediator in the development of bone formation and associated diseases. In the present review, the proposed mechanisms underlying the roles of MEG3 in osteogenic differentiation and its potential effects on bone diseases are discussed. These discussions may help elucidate the roles of MEG3 in osteogenic differentiation and highlight potential biomarkers and therapeutic targets for the treatment of bone diseases.

MEG3 regulates apoptosis of adipose‑derived stem cells

In plastic surgery, the maneuverability and safety of autologous fat transplantation have become increasingly recognized and continuously improved. However, the uncertainty of adipocyte survival makes it difficult to predict postoperative effects. Adipose‑derived stem cells (ADSCs) exhibit remarkable paracrine activity, and the number of ADSCs in adipose tissue is closely related to tissue survival. Maternally expressed gene 3 (MEG3) is known to modulate the apoptosis of various cell types. The present study aimed to evaluate the hypothesis that MEG3 serves an important role in ADSC apoptosis by regulating the expression of p53, and to explore the regulatory mechanisms of p53 in ADSC apoptosis. MEG3 was overexpressed in ADSCs and these cells were evaluated for viability, TP53 expression, apoptosis, morphology, and Bax and Bcl‑2 expression by performing MTT assays, reverse transcription‑quantitative PCR, flow cytometry analysis and western blotting. This study demonstrated that MEG3 may have an important role in the spontaneous apoptosis of ADSCs, and apoptosis induced by oxidative stress. In addition, this study revealed that p53 had a regulatory role in the downstream Bcl‑2/Bax pathway. This study provides insight into the role of MEG3 in ADSC apoptosis, thereby facilitating the survival of ADSCs during adipose tissue transplantation. Further in vivo and in vitro experiments should be conducted, along with the development of clinical applications.

Lnc-MAP6-1:3 knockdown inhibits osteosarcoma progression by modulating Bax/Bcl-2 and Wnt/β-catenin pathways

Osteosarcoma (OS) is the most common type of malignant bone tumor that affects children and adolescents. Still, the cellular and molecular mechanisms driving the development of this disease remain poorly understood. In this study, numerous dysregulated lncRNAs were identified by RNA-seq. As a result, we were able to find a novel lncRNA Lnc-MAP6-1:3 which is highly expressed in osteosarcoma. Using a set of approaches including gene knockdown, RT-PCR, oncogenic function assay and western blotting, we observed that knockdown of Lnc-MAP6-1:3 expression suppressed cell proliferation and colony formation, and promoted apoptosis in vitro. For the first time, we have identified that Lnc-MAP6-1:3 potentially influence the malignant behavior of osteosarcoma via Bax/Bcl-2 and Wnt/β-catenin signaling pathways. Henceforth, Lnc-MAP6-1:3 may provide a new molecular route of research and therapeutic applications for the diagnosis and treatment of osteosarcoma.

Functional impact of the long non-coding RNA MEG3 deletion by CRISPR/Cas9 in the human triple negative metastatic Hs578T cancer cell line

Long non-coding RNAs (lncRNAs) serve critical roles in regulating cellular homeostasis, and their deregulated expression/activity is associated with neoplastic transformation. The maternally expressed gene 3 (MEG3) has been extensively described as a tumor suppressor gene in different types of cancer, including breast cancer. Interestingly, using a panel of seven different breast cancer cell lines, the present study revealed that MEG3 is highly expressed in the triple negative metastatic human Hs578T breast cancer cell line, which is refractory to different therapeutic approaches. Therefore, the present study aimed to investigate the phenotypic impact of MEG3 deletion in this cell line. Using the CRISPR/Cas9 system, complete knockout (KO) of MEG3 was achieved. Deletion was confirmed by genomic PCR and reverse transcription-quantitative PCR. The MEG3_KO cell population displaying the highest efficiency of genomic editing was selected for phenotypic in vitro assays, including wound scratch and Transwell assays, flow cytometry and immunofluorescence. The results demonstrated that MEG3 deletion increased cell proliferation, anchorage-independent cell growth and cell motility, which was consistent with its well-known tumor suppressor function. However, the present study revealed that MEG3_KO also lead to decreased cell invasiveness ability, supporting previous evidence that MEG3 modulates epithelial-to-mesenchymal inducing factors. The present study demonstrated that deletion of MEG3 promoted an increase in transforming growth factor β and N-cadherin protein levels and significant reduction in matrix metallopeptidase 2, zinc-finger E-box binding homeobox 1 and collagen type III α1 chain gene expression levels. Additionally, MEG3_KO cells displayed significant resistance to doxorubicin treatment, demonstrating the role of this lncRNA in cancer cell survival by regulating apoptosis. The present study highlighted the utility of CRISPR/Cas9 for anticancer studies of intergenic lncRNAs and demonstrated that, although Hs578T cells express MEG3 at high levels, these cells display mechanisms to escape the growth suppression effects of this lncRNA. Notably, the detailed pathological mechanisms of MEG3 concerning tumor metastasis remain to be elucidated prior to applying MEG3 expression/activation in future therapeutic approaches for breast cancer treatment.

Non-Coding RNAs in Pediatric Solid Tumors

Pediatric solid tumors are a diverse group of extracranial solid tumors representing approximately 40% of childhood cancers. Pediatric solid tumors are believed to arise as a result of disruptions in the developmental process of precursor cells which lead them to accumulate cancerous phenotypes. In contrast to many adult tumors, pediatric tumors typically feature a low number of genetic mutations in protein-coding genes which could explain the emergence of these phenotypes. It is likely that oncogenesis occurs after a failure at many different levels of regulation. Non-coding RNAs (ncRNAs) comprise a group of functional RNA molecules that lack protein coding potential but are essential in the regulation and maintenance of many epigenetic and post-translational mechanisms. Indeed, research has accumulated a large body of evidence implicating many ncRNAs in the regulation of well-established oncogenic networks. In this review we cover a range of extracranial solid tumors which represent some of the rarer and enigmatic childhood cancers known. We focus on two major classes of ncRNAs, microRNAs and long non-coding RNAs, which are likely to play a key role in the development of these cancers and emphasize their functional contributions and molecular interactions during tumor formation.

lncRNA MEG3 inhibits the growth of hepatocellular carcinoma cells by sponging miR-9-5p to upregulate SOX11

The long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3), a tumor suppressor, is critical for the carcinogenesis and progression of different cancers, including hepatocellular carcinoma (HCC). To date, the roles of lncRNA MEG3 in HCC are not well illustrated. Therefore, this study used western blot and qRT-PCR to evaluate the expression of MEG3, miR-9-5p, and Sex determining Region Y-related HMG-box 11 (SOX11) in HCC tissues and cell lines. RNA pull-down and luciferase reporter assay were used to evaluate these molecular interactions. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry detected the viability and apoptosis of HCC cells, respectively. The results showed that MEG3 and SOX11 were poorly expressed but miR-9-5p was highly expressed in HCC. The expression levels of these molecules suggested a negative correlation between MEG3 and miR-9-5p and a positive correlation with SOX11, confirmed by Pearson's correlation analysis and biology experiments. Furthermore, MEG3 could combine with miR-9-5p, and SOX11 was a direct target of miR-9-5p. Moreover, MEG3 over-expression promoted cell apoptosis and growth inhibition in HCC cells through sponging miR-9-5p to up-regulate SOX11. Therefore, the interactions among MEG3, miR-9-5p, and SOX11 might offer a novel insight for understanding HCC pathogeny and provide potential diagnostic markers and therapeutic targets for HCC.

Deregulated lncRNA expression profile in the mouse lung adenocarcinomas with KRAS-G12D mutation and P53 knockout

Recent studies have demonstrated that aberrant long non‐coding RNAs (lncRNAs) expression are suggested to be closely associated with multiple human diseases, lung cancer included. However, the roles of lncRNAs in lung cancer are not well understood. In this study, we used microarrays to investigate the aberrantly expressed lncRNAs in the mouse lung adenocarcinoma with P53 knockout and the Kras^G12D mutation. Results revealed that 6424 lncRNAs were differentially expressed (≥ 2‐fold change, P < .05). Two hundred and ten lncRNAs showed more than 8‐fold change and conserved across human and were further analysed in the primary mouse lung adenocarcinoma KP cells, which were isolated from the p53 knockout and the Kras^G12D mutation mice. Among all the 210 lncRNAs, 11 lncRNAs' expression was regulated by P53, 33 lncRNAs by KRAS and 13 lncRNAs by hypoxia in the primary KP cells, respectively. NONMMUT015812, which was remarkably up‐regulated in the mouse lung adenocarcinoma and negatively regulated by the P53 re‐expression, was detected to analyse its cellular function. Results showed that knockdown of NONMMUT015812 by shRNAs decreased proliferation and migration abilities of KP cells. Among those aberrantly expressed lncRNAs in the mouse lung adenocarcinoma, NONMMUT015812 was a potential oncogene.

Long non-coding RNA ENST00000500843 is downregulated and promotes chemoresistance to paclitaxel in lung adenocarcinoma

Adenocarcinoma is one of the most common pathological types of human lung cancer and has the highest incidence and mortality rates worldwide. Resistance to paclitaxel (PTX), the standard chemotherapy agent for treatment of lung adenocarcinoma, is a major clinical obstacle. Sensitive markers are urgently required for the diagnosis and characterization of lung cancer, as well as to manage drug resistance. Previous studies have described the activity of long non-coding RNAs (lncRNAs) in human lung cancer and chemotherapy resistance. In previous studies, lncRNA ENST00000500843 was identified to be downregulated in PTX-resistant A549 human lung cancer cells. However, the roles of this lncRNA in the development of lung adenocarcinoma and its mechanism in PTX resistance, to the best of our knowledge, have not been described. In the present study, 56 pairs of lung adenocarcinoma and normal adjacent tissue samples were collected. Reverse transcription-quantitative PCR revealed that the expression levels of lncRNA ENST00000500843 were lower in lung adenocarcinoma tissues and PTX-resistant A549 cells when compared with normal adjacent tissues and A549 cells. Decreased expression levels of lncRNA ENST00000500843 in lung adenocarcinoma tissues were associated with tumor diameter, the degree of pathological differentiation and metastasis of lymph nodes. Additionally, patients with low expression levels of ENST00000500843 exhibited poorer overall survival and progression-free survival rates. Furthermore, the present study demonstrated that knockdown of lncRNA ENST00000500843 with small interfering RNA decreased the likelihood of apoptosis in A549 cells and promoted resistance to PTX. This indicated that lncRNA ENST00000500843 may be a useful diagnostic marker of lung cancer and a good prognostic marker for resistance to treatment with PTX.

The Role of Non-Coding RNAs Involved in Nickel-Induced Lung Carcinogenic Mechanisms

Nickel is a naturally occurring element found in the Earth’s crust and an International Agency for Research on Cancer (IARC)-classified human carcinogen. While low levels found in the natural environment pose a minor concern, the extensive use of nickel in industrial settings such as in the production of stainless steel and various alloys complicate human exposure and health effects. Notably, interactions with nickel macromolecules, primarily through inhalation, have been demonstrated to promote lung cancer. Mechanisms of nickel-carcinogenesis range from oxidative stress, DNA damage, and hypoxia-inducible pathways to epigenetic mechanisms. Recently, non-coding RNAs have drawn increased attention in cancer mechanistic studies. Specifically, nickel has been found to disrupt expression and functions of micro-RNAs and long-non-coding RNAs, resulting in subsequent changes in target gene expression levels, some of which include key cancer genes such as p53, MDM2, c-myc, and AP-1. Non-coding RNAs are also involved in well-studied mechanisms of nickel-induced lung carcinogenesis, such as the hypoxia-inducible factor (HIF) pathway, oxidative stress, DNA damage and repair, DNA hypermethylation, and alterations in tumor suppressors and oncogenes. This review provides a summary of the currently known epigenetic mechanisms involved in nickel-induced lung carcinogenesis, with a particular focus on non-coding RNAs.

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.

Regulatory effects of lncRNAs and miRNAs on autophagy in malignant tumorigenesis

Autophagy is an important process in endogenous substrate degradation by lysosomes within cells, with a degree of evolutionary conservation. Like apoptosis and cell senescence, cell autophagy is a very important biological phenomenon involving the development and growth of biological processes. Abnormal autophagy may lead to tumorigenesis. In recent years, increasing studies have demonstrated that long non-coding RNAs (lncRNAs) and miRNAs can regulate cell autophagy by modulating targetting gene expression. In this review, we will provide an overview of lncRNAs and miRNAs in autophagy modulation and new insights into the underlying mechanisms, as well as their potential utilization in disease diagnosis, prognosis, and therapy.