Regulation of tumor cell migration and invasion by the H19/let-7 axis is antagonized by metformin-induced DNA methylation

H19 lncRNA alters stromal cell growth via IGF signaling in the endometrium of women with endometriosis

Endometriosis affects approximately 15% of reproductive aged women and is associated with chronic pelvic pain and infertility. However, the molecular mechanisms by which endometriosis impacts fertility are poorly understood. The developmentally regulated, imprinted H19 long noncoding RNA (lncRNA) functions to reduce the bioavailability of microRNA let-7 by acting as a molecular sponge. Here we report that H19 expression is significantly decreased in the eutopic endometrium of women with endometriosis as compared to normal controls. We show that decreased H19 increases let-7 activity, which in turn inhibits Igf1r expression at the post-transcriptional level, thereby contributing to reduced proliferation of endometrial stromal cells. We propose that perturbation of this newly identified H19/Let-7/IGF1R regulatory pathway may contribute to impaired endometrial preparation and receptivity for pregnancy in women with endometriosis. Our finding represents the first example of a lncRNA-based mechanism in endometriosis and its associated infertility, thus holding potential in the development of novel therapeutics for women with endometriosis and infertility.

H19 Long Noncoding RNA Regulates Intestinal Epithelial Barrier Function via MicroRNA 675 by Interacting with RNA-Binding Protein HuR

The disruption of the intestinal epithelial barrier function occurs commonly in various pathologies, but the exact mechanisms responsible are unclear. The H19 long noncoding RNA (lncRNA) regulates the expression of different genes and has been implicated in human genetic disorders and cancer. Here, we report that H19 plays an important role in controlling the intestinal epithelial barrier function by serving as a precursor for microRNA 675 (miR-675). H19 overexpression increased the cellular abundance of miR-675, which in turn destabilized and repressed the translation of mRNAs encoding tight junction protein ZO-1 and adherens junction E-cadherin, resulting in the dysfunction of the epithelial barrier. Increasing the level of the RNA-binding protein HuR in cells overexpressing H19 prevented the stimulation of miR-675 processing from H19, promoted ZO-1 and E-cadherin expression, and restored the epithelial barrier function to a nearly normal level. In contrast, the targeted deletion of HuR in intestinal epithelial cells enhanced miR-675 production in the mucosa and delayed the recovery of the gut barrier function after exposure to mesenteric ischemia/reperfusion. These results indicate that H19 interacts with HuR and regulates the intestinal epithelial barrier function via the H19-encoded miR-675 by altering ZO-1 and E-cadherin expression posttranscriptionally.

RNA-binding protein IGF2BP3 targeting of oncogenic transcripts promotes hematopoietic progenitor proliferation

Posttranscriptional control of gene expression is important for defining both normal and pathological cellular phenotypes. In vitro, RNA-binding proteins (RBPs) have recently been shown to play important roles in posttranscriptional regulation; however, the contribution of RBPs to cell specification is not well understood. Here, we determined that the RBP insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is specifically overexpressed in mixed lineage leukemia-rearranged (MLL-rearranged) B-acute lymphoblastic leukemia (B-ALL), which constitutes a subtype of this malignancy associated with poor prognosis and high risk of relapse. IGF2BP3 was required for the survival of B-ALL cell lines, as knockdown led to decreased proliferation and increased apoptosis. Enforced expression of IGF2BP3 provided murine BM cells with a strong survival advantage, led to proliferation of hematopoietic stem and progenitor cells, and skewed hematopoietic development to the B cell/myeloid lineage. Cross-link immunoprecipitation and high throughput sequencing uncovered the IGF2BP3-regulated transcriptome, which includes oncogenes MYC and CDK6 as direct targets. IGF2BP3 regulated transcripts via targeting elements within 3' untranslated regions (3'UTR), and enforced IGF2BP3 expression in mice resulted in enhanced expression of Myc and Cdk6 in BM. Together, our data suggest that IGF2BP3-mediated targeting of oncogenic transcripts may represent a critical pathogenetic mechanism in MLL-rearranged B-ALL and support IGF2BP3 and its cognate RNA-binding partners as potential therapeutic targets in this disease.

Long noncoding RNAs related to the odontogenic potential of dental mesenchymal cells in mice

OBJECTIVES

The purpose of this study is to identify the lncRNAs that are associated with the odontogenic potential in mouse dental mesenchymal cells.

DESIGN

The odontogenic potential of dental mesenchymal cells was found to be lost in the course of in vitro culture, so the lncRNA profiles were subsequently compared between freshly-isolated and cultured dental mesenchymal cells using RNA-sequencing. A co-expression analysis of differentially expressed lncRNAs and coding RNAs was performed to understand their potential functions. The expression of several selected lncRNAs was also examined in developing tooth germs.

RESULTS

Compared with cultured dental mesenchymal cells, 108 lncRNAs were upregulated and 36 lncRNAs were downregulated in freshly-isolated dental mesenchymal cells. Coding genes correlated with the lncRNAs were mainly associated with DNA and protein metabolic processes and cytoskeletal anchorage. Meg3, Malat1, Xist, and Dlx1as were significantly downregulated in cultured dental mesenchymal cells but were upregulated in odontogenic dental mesenchymal tissues. Moreover, the levels of Dlx1as were negatively correlated with that of Dlx1 in dental mesenchymal cells and dental mesenchymal tissues.

CONCLUSIONS

The lncRNA profiles of dental mesenchymal cells are significantly changed during culturing, and the dysregulation of lncRNAs is associated with the loss of odontogenic potential.

Functional diversity of long non-coding RNAs in immune regulation

Precise and dynamic regulation of gene expression is a key feature of immunity. In recent years, rapid advances in transcriptome profiling analysis have led to recognize long non-coding RNAs (lncRNAs) as an additional layer of gene regulation context. In the immune system, lncRNAs are found to be widely expressed in immune cells including monocytes, macrophages, dendritic cells (DC), neutrophils, T cells and B cells during their development, differentiation and activation. However, the functional importance of immune-related lncRNAs is just emerging to be characterized. In this review, we discuss the up-to-date knowledge of lncRNAs in immune regulation.

The role of the oncofetal H19 lncRNA in tumor metastasis: orchestrating the EMT-MET decision

Long non-coding RNA (lncRNA) genes are emerging as key players in the metastatic cascade. Current evidence indicate that H19 lncRNA and the microRNA(miRNA) miR-675, which is processed from it, play crucial roles in metastasis, through the regulation of critical events specifically the epithelial to mesenchymal (EMT) and the mesenchymal to epithelial transitions (MET). This review summarizes recent mechanistic pathways and tries to put together seemingly conflicting data from different reports under one proposed general scheme underlying the various roles of H19/miR-675 in the metastatic cascade. We propose several approaches to harnessing this knowledge for translational medicine.

Milk: an epigenetic amplifier of FTO-mediated transcription? Implications for Western diseases

Single-nucleotide polymorphisms within intron 1 of the FTO (fat mass and obesity-associated) gene are associated with enhanced FTO expression, increased body weight, obesity and type 2 diabetes mellitus (T2DM). The N⁶-methyladenosine (m⁶A) demethylase FTO plays a pivotal regulatory role for postnatal growth and energy expenditure. The purpose of this review is to provide translational evidence that links milk signaling with FTO-activated transcription of the milk recipient. FTO-dependent demethylation of m⁶A regulates mRNA splicing required for adipogenesis, increases the stability of mRNAs, and affects microRNA (miRNA) expression and miRNA biosynthesis. FTO senses branched-chain amino acids (BCAAs) and activates the nutrient sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1), which plays a key role in translation. Milk provides abundant BCAAs and glutamine, critical components increasing FTO expression. CpG hypomethylation in the first intron of FTO has recently been associated with T2DM. CpG methylation is generally associated with gene silencing. In contrast, CpG demethylation generally increases transcription. DNA de novo methylation of CpG sites is facilitated by DNA methyltransferases (DNMT) 3A and 3B, whereas DNA maintenance methylation is controlled by DNMT1. MiRNA-29s target all DNMTs and thus reduce DNA CpG methylation. Cow´s milk provides substantial amounts of exosomal miRNA-29s that reach the systemic circulation and target mRNAs of the milk recipient. Via DNMT suppression, milk exosomal miRNA-29s may reduce the magnitude of FTO methylation, thereby epigenetically increasing FTO expression in the milk consumer. High lactation performance with increased milk yield has recently been associated with excessive miRNA-29 expression of dairy cow mammary epithelial cells (DCMECs). Notably, the galactopoietic hormone prolactin upregulates the transcription factor STAT3, which induces miRNA-29 expression. In a retrovirus-like manner milk exosomes may transfer DCMEC-derived miRNA-29s and bovine FTO mRNA to the milk consumer amplifying FTO expression. There is compelling evidence that obesity, T2DM, prostate and breast cancer, and neurodegenerative diseases are all associated with increased FTO expression. Maximization of lactation performance by veterinary medicine with enhanced miRNA-29s and FTO expression associated with increased exosomal miRNA-29 and FTO mRNA transfer to the milk consumer may represent key epigenetic mechanisms promoting FTO/mTORC1-mediated diseases of civilization.

H19 lncRNA alters DNA methylation genome wide by regulating S-adenosylhomocysteine hydrolase

DNA methylation is essential for mammalian development and physiology. Here we report that the developmentally regulated H19 lncRNA binds to and inhibits S-adenosylhomocysteine hydrolase (SAHH), the only mammalian enzyme capable of hydrolysing S-adenosylhomocysteine (SAH). SAH is a potent feedback inhibitor of S-adenosylmethionine (SAM)-dependent methyltransferases that methylate diverse cellular components, including DNA, RNA, proteins, lipids and neurotransmitters. We show that H19 knockdown activates SAHH, leading to increased DNMT3B-mediated methylation of an lncRNA-encoding gene Nctc1 within the Igf2-H19-Nctc1 locus. Genome-wide methylation profiling reveals methylation changes at numerous gene loci consistent with SAHH modulation by H19. Our results uncover an unanticipated regulatory circuit involving broad epigenetic alterations by a single abundantly expressed lncRNA that may underlie gene methylation dynamics of development and diseases and suggest that this mode of regulation may extend to other cellular components.

The growth arrest-specific transcript 5 (GAS5): a pivotal tumor suppressor long noncoding RNA in human cancers

Long noncoding RNAs (lncRNAs), which refer to a group of RNAs with length more than 200 nucleotides and limited protein-coding potential, play a widespread role in regulating biological processes, such as cell differentiation, proliferation, apoptosis, and migration. LncRNAs are dysregulated in multiple cancers, playing an either oncogenic or tumor-suppressive role. LncRNA GAS5 is a recently identified tumor suppressor involved in several cancers, like breast cancer, prostate cancer, lung cancer, and colorectal cancer. The low-expression pattern confers tumor cells elevated capacity of proliferation and predicts poorer prognosis. Existing studies mirror that lncRNA GAS5 promises to be a novel diagnostic biomarker, therapy target, as well as prognostic biomarker. In this review, we will summarize the current knowledge about this vital lncRNA, from its discovery, characteristics, and biological function to molecular mechanism in various neoplasms.

The interplay of long non-coding RNAs and MYC in cancer

Long non-coding RNAs (lncRNAs) are a class of RNA molecules that are changing how researchers view eukaryotic gene regulation. Once considered to be non-functional products of low-level aberrant transcription from non-coding regions of the genome, lncRNAs are now viewed as important epigenetic regulators and several lncRNAs have now been demonstrated to be critical players in the development and/or maintenance of cancer. Similarly, the emerging variety of interactions between lncRNAs and MYC, a well-known oncogenic transcription factor linked to most types of cancer, have caught the attention of many biomedical researchers. Investigations exploring the dynamic interactions between lncRNAs and MYC, referred to as the lncRNA-MYC network, have proven to be especially complex. Genome-wide studies have shown that MYC transcriptionally regulates many lncRNA genes. Conversely, recent reports identified lncRNAs that regulate MYC expression both at the transcriptional and post-transcriptional levels. These findings are of particular interest because they suggest roles of lncRNAs as regulators of MYC oncogenic functions and the possibility that targeting lncRNAs could represent a novel avenue to cancer treatment. Here, we briefly review the current understanding of how lncRNAs regulate chromatin structure and gene transcription, and then focus on the new developments in the emerging field exploring the lncRNA-MYC network in cancer.

The H19 Long non-coding RNA in cancer initiation, progression and metastasis - a proposed unifying theory

The imprinted oncofetal long non-coding RNA (lncRNA) H19 is expressed in the embryo, down-regulated at birth and then reappears in tumors. Its role in tumor initiation and progression has long been a subject of controversy, although accumulating data suggest that H19 is one of the major genes in cancer. It is actively involved in all stages of tumorigenesis and is expressed in almost every human cancer. In this review we delineate the various functions of H19 during the different stages in the complex process of tumor progression. H19 up-regulation allows cells to enter a "selfish" survival mode in response to stress conditions, such as destabilization of the genome and hypoxia, by accelerating their proliferation rate and increasing overall cellular resistance to stress. This response is tightly correlated with nullification, dysfunction or significant down-regulation of the master tumor suppressor gene P53. The growing evidence of H19's involvement in both proliferation and differentiation processes, together with its involvement in epithelial to mesenchymal transition (EMT) and also mesenchymal to epithelial transition (MET), has led us to conclude that some of the recent disputes and discrepancies arising from current research findings can be resolved from a viewpoint supporting the oncogenic properties of H19. According to a holistic approach, the versatile, seemingly contradictory functions of H19 are essential to, and differentially harnessed by, the tumor cell depending on its context within the process of tumor progression.

When Anti-Aging Studies Meet Cancer Chemoprevention: Can Anti-Aging Agent Kill Two Birds with One Blow?

Recent evidence has strongly supported that the rate of aging is controlled, at least to some extent, by evolutionarily conserved nutrient sensing pathways (e.g. the insulin/IGF-1-signaling, mTOR, AMPK, and sirtuins) from worms to humans. These pathways are also commonly involved in carcinogenesis and cancer metabolism. Agents (e.g. metformin, resveratrol, and Rhodiola) that target these nutrient sensing pathways often have both anti-aging and anti-cancer efficacy. These agents not only reprogram energy metabolism of malignant cells, but also target normal postmitotic cells by suppressing their conversion into senescent cells, which confers systematic metabolism benefits. These agents are fundamentally different from chemotherapy (e.g. paclitaxel and doxorubicin) or radiation therapy that causes molecular damage (e.g. DNA and protein damages) and thereby no selection resistance may be expected. By reviewing molecular mechanisms of action, epidemiological evidence, experimental data in tumor models, and early clinical study results, this review provides information supporting the promising use of agents with both anti-aging and anti-cancer efficacy for cancer chemoprevention.

Long Non-Coding RNAs: New Players in Hematopoiesis and Leukemia

Long non-coding RNAs (lncRNAs) are important regulators of gene expression that influence almost every step in the life cycle of genes, from transcription to mRNA splicing, RNA decay, and translation. Besides their participation to normal physiology, lncRNA expression and function have been already associated to cancer development and progression. Here, we review the functional role and mechanisms of action of lncRNAs in normal hematopoiesis and how their misregulation may be implicated in the development of blood cell cancer, such as leukemia.

The non-coding RNAs of the H19-IGF2 imprinted loci: a focus on biological roles and therapeutic potential in Lung Cancer

Since it was first described, the imprinted cluster 11p15.5 has been reported to be deregulated in a variety of pediatric and adult cancers including that of the lung. Both protein coding and non-coding genes functioning as oncogenes or as tumor suppressor genes reside within this cluster. Oncomirs that can function as oncogenes or as tumor suppressors have also been reported. While a complete account of the role played by the 11p15.5 imprinted cluster in lung cancer is beyond the scope of this review, we will focus on the role of the non-coding RNAs processed from the H19-IGF2 loci. A special emphasis will be given to the H19/miR-675 gene locus. Their potential diagnostic and therapeutic use in lung cancer will be described.

Association of polymorphisms in long non-coding RNA H19 with coronary artery disease risk in a Chinese population

H19 is an imprinted gene transcribing a long non-coding RNA and is downregulated postnatally. Re-expression of H19 has been observed in patients with atherosclerosis. However, to date, no data has been published on the association of H19 polymorphisms with the risk of coronary artery disease (CAD). In this study, four polymorphisms, rs217727, rs2067051, rs2251375, rs4929984, were analyzed in 701 CAD patients and 873 age- and sex-matched control subjects. Polymorphisms were genotyped by TaqMan technology. Our data showed that the T variant of rs217727 was associated with an increased risk of CAD [additive model: odds ratio (OR)=2.05, 95%CI=1.35-3.12; dominant model: OR=1.46, 95% confidence interval (CI)=1.12-1.90; recessive model: OR=1.75, 95%CI=1.18-2.58], while A variant of rs2067051 was associated with a decreased risk of CAD (additive model: OR=0.66, 95%CI=0.45-0.96; recessive model: OR=0.71, 95%CI=0.50-0.99). Combined analysis showed that subjects carrying 3 or 4 risk alleles had a significantly increased risk of CAD, relative to those with 0-2 risk alleles (OR=1.61, 95%CI=1.20-2.15). Moreover, CAD patients with 3 or 4 risk alleles also had significantly higher Gensini scores than those with 0-2 risk alleles (P=0.001). Further haplotype-based analysis revealed that individuals with C-G-C-C, T-G-A-A, and T-A-A-A haplotypes indicated a higher prevalence of CAD (OR=1.88, 95%CI=1.03-3.43; OR=2.26, 95%CI=1.19-4.31; OR=2.66, 95%CI=1.34-5.25, respectively), compared to individuals with the most common C-G-A-C haplotype. In conclusion, our study demonstrates for the first time that common polymorphisms of H19 are associated with the risk and severity of CAD in a Chinese population. Future studies are needed to explore the underlying mechanisms of our findings.

Obesity is associated with a decrease in expression but not with the hypermethylation of thermogenesis-related genes in adipose tissues

Background

Impaired thermogenesis can promote obesity. Therefore, the aim of this study was to investigate whether the expression of thermogenesis-related genes is altered in adipose tissues of obese individuals and whether excessive methylation of their promoters is involved in this phenomenon.

Methods

The expression of genes encoding β adrenergic receptors (ADRBs), thyroid hormone receptors (THRs), 5’-iodothyronine deiodinases (DIOs), and uncoupling proteins (UCPs) was measured by real-time PCR in visceral and in subcutaneous adipose tissues of 58 obese (BMI >40 kg/m²) and 50 slim (BMI 20-24.9 kg/m²) individuals. The methylation status of these genes was studied by the methylation-sensitive digestion/real-time PCR method.

Results

The expression of ADRB2, ADRB3, THRA, THRB, DIO2, UCP2 was significantly lower in the adipose tissues of obese patients than in tissues of normal-weight individuals (P < 0.00001). In the obese, the expression of ADRB2, ADRB3, DIO2 was lower in visceral adipose tissue than in subcutaneous adipose tissue (P = 0.008, P = 0.002, P = 0.001, respectively). However, the mean methylation of CpG islands of these genes was similar in tissues with their high and low expression, and there was no correlation between the level of expression and the level of methylation.

Conclusions

Decreased expression of thermogenesis-related genes in adipose tissues of obese patients might result in the reduced reactivity to both hormonal and adrenergic stimuli and therefore in a lower potential to activate thermogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0395-2) contains supplementary material, which is available to authorized users.

The H19/let-7 double-negative feedback loop contributes to glucose metabolism in muscle cells

The H19 lncRNA has been implicated in development and growth control and is associated with human genetic disorders and cancer. Acting as a molecular sponge, H19 inhibits microRNA (miRNA) let-7. Here we report that H19 is significantly decreased in muscle of human subjects with type-2 diabetes and insulin resistant rodents. This decrease leads to increased bioavailability of let-7, causing diminished expression of let-7 targets, which is recapitulated in vitro where H19 depletion results in impaired insulin signaling and decreased glucose uptake. Furthermore, acute hyperinsulinemia downregulates H19, a phenomenon that occurs through PI3K/AKT-dependent phosphorylation of the miRNA processing factor KSRP, which promotes biogenesis of let-7 and its mediated H19 destabilization. Our results reveal a previously undescribed double-negative feedback loop between sponge lncRNA and target miRNA that contributes to glucose regulation in muscle cells.