Involvement of epigenetically silenced microRNA-181c in gastric carcinogenesis

A MiR181/Sirtuin1 regulatory circuit modulates drug response in biliary cancers

Despite recent advances, biliary tract cancer (BTC) remains one of the most lethal tumor worldwide due to late diagnosis, limited therapeutic strategies and resistance to conventional therapies. In recent years, high-throughput technologies have enabled extensive genome, and transcriptome sequencing unveiling, among others, the regulatory potential of microRNAs (miRNAs). Compelling evidence shown that miRNA are attractive therapeutic targets and promising candidates as biomarkers for various therapy-resistant tumors. The analysis of miRNA profile successfully identified miR-181c and -181d as significantly downregulated in BTC patients. Low miR-181c and -181d expression levels were correlated with worse prognosis and poor treatment efficacy. In fact, progression-free survival analysis indicated poor survival rates in miR-181c and -181d low expressing patients. The expression profile of miR-181c and -181d in BTC cell lines revealed that both miRNAs were dysregulated. Functional in vitro experiments in BTC cell lines showed that overexpression of miR-181c and -181d affected cell viability and increased sensitivity to chemotherapy compared to controls. In addition, by using bioinformatic tools we showed that the miR-181c/d functional role is determined by binding to their target SIRT1 (Sirtuin 1). Moreover, BTC patients expressing high levels of miR-181 and low SIRT1 shown an improved survival and treatment response. An integrative network analysis demonstrated that, miR-181/SIRT1 circuit had a regulatory effect on several important metabolic tumor-related processes. Our study demonstrated that miR-181c and -181d act as tumor suppressor miRNA in BTC, suggesting the potential use as therapeutic strategy in resistant cancers and as predictive biomarker in the precision medicine of BTC.

Ectopic expression of tumor suppressive miR-181c-5p downregulates oncogenic Notch signaling in MDA-MB-231 cells

Triple negative breast cancer (TNBC) is a very invasive subtype of breast cancer (BCa), this is accounted for 15-20% of all BCa cases. TNBC patients have very limited therapy option due to lack of effective targets and patients shows the worse survival. Therefore, present study has tried to introduce the target based therapy by studying the tumor suppressive role of miR-181c-5p on oncogenic Notch1 signaling. Transient transfection, bioinformatics, qRT-PCR, Notch1 luciferase assay and western blotting techniques were utilized to study the effect of induced expression of miR-181c-5p on oncogenic Notch1 signaling in MDA-MB-231 cells. Results shows that miR-181c-5p mimic increase the expression of miR-181c-5p by 45.26% and 75.96% in 24 and 48 h incubation, respectively (p < 0.0003) in transfected cells. The miR-181c-5p binds at NOTCH1 3' UTR target binding site with a minimum free energy of - 26.0 kcal/mol. The AGO protein showed significant interaction with the miR-181c-5p and miR-181c-5p-NOTCH1 complex. Decreased expression of NOTCH1 by 32.88% and 45.87% (p < 0.0001); and HES1 expression by 14.06% and 53.24% (p < 0.0001) was observed in 24 and 48 h transfected cells respectively. Notch1 promoter luciferase activity was reduced by 25.72% and 46.98% in 24 and 48 h miRNA-mimic transfected cells. Western blot analysis also showed significant reduction in NOTCH1 and HES1 proteins expression. In conclusion, present study suggests that the forced expression of tumor suppressive miR-181c-5p negatively regulates oncogenic Notch1 signaling in TNBC. Negative regulation of Notch1 signaling via miR-181c-5p mimic could be a hopeful therapeutic strategy in TNBC patient treatment.

Mechanisms Controlling MicroRNA Expression in Tumor

MicroRNAs (miRNAs) are widely present in many organisms and regulate the expression of genes in various biological processes such as cell differentiation, metabolism, and development. Numerous studies have shown that miRNAs are abnormally expressed in tumor tissues and are closely associated with tumorigenesis. MiRNA-based cancer gene therapy has consistently shown promising anti-tumor effects and is recognized as a new field in cancer treatment. So far, some clinical trials involving the treatment of malignancies have been carried out; however, studies of miRNA-based cancer gene therapy are still proceeding slowly. Therefore, furthering our understanding of the regulatory mechanisms of miRNA can bring substantial benefits to the development of miRNA-based gene therapy or other combination therapies and the clinical outcome of patients with cancer. Recent studies have revealed that the aberrant expression of miRNA in tumors is associated with promoter sequence mutation, epigenetic alteration, aberrant RNA modification, etc., showing the complexity of aberrant expression mechanisms of miRNA in tumors. In this paper, we systematically summarized the regulation mechanisms of miRNA expression in tumors, with the aim of providing assistance in the subsequent elucidation of the role of miRNA in tumorigenesis and the development of new strategies for tumor prevention and treatment.

Diagnosis value of miR-181, miR-652, and CA72-4 for gastric cancer

PURPOSE

To find a useful disease marker for early diagnosis of gastric cancer, we tried to explore the expression of serum miR-181, miR-652, and carbohydrate antigen 72-4 (CA72-4).

PATIENTS AND METHODS

According to clinical pathologic stages, 112 patients with gastric cancer were divided into early gastric cancer group (n = 60) and advanced gastric cancer group (n = 52), stage I-II (n = 65), and stage III-IV (n = 47). Another 50 cases of gastric benign lesions and 40 healthy controls were also selected. Real-time quantitative PCR together with chemiluminescence were applied to detect expression levels. ROC curve was applied to judge their diagnostic efficiency. Pearson's correlation analysis was put into use to investigate the relevance of three indicators.

RESULTS

Compared with benign lesions group and control group, significantly higher expression levels were found in patients of gastric cancer (all p < 0.001). Similarly, compared with early gastric cancer group, significantly higher expression levels were found in advanced gastric cancer group (all p < 0.001). The same result was also found in stage III-IV (all p < 0.001). The best cutoff values were 0.93, 2.38, and 16.94 U/ml, respectively. The area under the curve (0.917, 95%CI: 0.856-0.975) of the three combined diagnosis of early gastric cancer was the largest, and its sensitivity and specificity were 92.5% and 86.8%. And miR-181 and miR-652 were positively correlated with CA72-4 (r = 0.772, p < 0.001, r = 0.853, p < 0.001).

CONCLUSION

Serum miR-181, miR-652, and CA72-4 are closely linked to the occurrence and development of gastric cancer. Combination of three indicators has diagnostic value for early gastric cancer.

miR-181c regulates MCL1 and cell survival in GATA2 deficient cells

GATA2 is a transcription factor critical for hematopoiesis. Germline mutations in GATA binding protein 2 (GATA2) led to haploinsufficiency, severe cytopenias of multiple cell lineages, susceptibility to infections and strong propensity to develop myelodysplastic syndrome, and acute myeloid leukemia. Mechanisms of progressive cytopenias remain unclear. MicroRNA (miRNA) represents a unique mechanism of post-transcriptional gene regulation. In this study, miRNA profiles were evaluated and eight miRNAs were found to be differentially expressed (≥2-fold, P ≤ 0.05) in patient-derived cell lines (N = 13) in comparison to controls (N = 10). miR-9, miR-181a-2-3p, miR-181c, miR-181c-3p, miR-486-3p, and miR-582 showed increased expression, whereas miR-223 and miR-424-3p showed decreased expression. Cell death assays indicated that miR-181c potently induces cell death in lymphoid (Ly-8 and SP-53) and myeloid (HL-60) cell lines. miR-181c was predicted to target myeloid cell leukemia (MCL)1, which was confirmed by transfection assays, resulting in significantly reduced MCL1 mRNA and decreased live cell numbers. Bone marrow analysis of 34 GATA2 patients showed significantly decreased cellularity, CD34-positive cells, monocytes, dendritic cells, NK cells, B cells, and B cell precursors in comparison to healthy controls (N = 29; P < 0.001 for each), which was accompanied by decreased levels of MCL1 (P < 0.05). GATA2 expression led to significant repression of miR-181c expression in transfection experiments. Conversely, knockdown of GATA2 led to increased miR-181c expression. These findings indicate that miR-181c expression is increased and MCL1 levels decreased in GATA2 deficiency cells, and that GATA2 represses miR-181c transcription. Increased miR-181c may contribute to elevated cell death and cytopenia in GATA2 deficiency potentially through down-regulation of MCL1.

Effect of Helicobacter pylori Eradication on Epigenetic Changes in Gastric Cancer-related Genes

It is known that gastric carcinogenesis results from the progressive changes from chronic gastritis to gastric atrophy, intestinal metaplasia, dysplasia, and invasive carcinoma. Several genetic and epigenetic alterations are involved in this process, and Helicobacter pylori (H. pylori) infection is believed to induce the initiation and progression of these steps. From an epigenetic point of view, H. pylori induces hypermethylation of genes involved in the development of gastric cancer and regulates the expression of various microRNAs (miRNAs). These H. pylori-related epigenetic changes are accumulated not only at the site of neoplasm but also in the adjacent non-cancerous gastric mucosa. Thereby, a state vulnerable to gastric cancer known as an epigenetic field defect is formed. H. pylori eradication can have an effective chemopreventive effect in gastric carcinogenesis. However, the molecular biological changes that occur in the stomach environment during H. pylori eradication have not yet been established. Several studies have reported that H. pylori eradication can restore infection-related changes, especially epigenetic alterations in gastric cancer-related genes, but some studies have shown otherwise. Simply put, it appears that the recovery of methylated gastric cancer-related genes and miRNAs during H. pylori eradication may vary among genes and may also differ depending on the histological subtype of the gastric mucosa. In this review, we will discuss the potential mechanism of gastric cancer prevention by H. pylori eradication, mainly from an epigenetic perspective.

Role of miR-181c in Diet-induced obesity through regulation of lipid synthesis in liver

We recently identified a nuclear-encoded miRNA (miR-181c) in cardiomyocytes that can translocate into mitochondria to regulate mitochondrial gene mt-COX1 and influence obesity-induced cardiac dysfunction through the mitochondrial pathway. Because liver plays a pivotal role during obesity, we hypothesized that miR-181c might contribute to the pathophysiological complications associated with obesity. Therefore, we used miR-181c/d^-/- mice to study the role of miR-181c in hepatocyte lipogenesis during diet-induced obesity. The mice were fed a high-fat (HF) diet for 26 weeks, during which indirect calorimetric measurements were made. Quantitative PCR (qPCR) was used to examine the expression of genes involved in lipid synthesis. We found that miR-181c/d^-/- mice were not protected against all metabolic consequences of HF exposure. After 26 weeks, the miR-181c/d^-/- mice had a significantly higher body fat percentage than did wild-type (WT) mice. Glucose tolerance tests showed hyperinsulinemia and hyperglycemia, indicative of insulin insensitivity in the miR-181c/d^-/- mice. miR-181c/d^-/- mice fed the HF diet had higher serum and liver triglyceride levels than did WT mice fed the same diet. qPCR data showed that several genes regulated by isocitrate dehydrogenase 1 (IDH1) were more upregulated in miR-181c/d^-/- liver than in WT liver. Furthermore, miR-181c delivered in vivo via adeno-associated virus attenuated the lipogenesis by downregulating these same lipid synthesis genes in the liver. In hepatocytes, miR-181c regulates lipid biosynthesis by targeting IDH1. Taken together, the data indicate that overexpression of miR-181c can be beneficial for various lipid metabolism disorders.

Targeting Notch4 in Cancer: Molecular Mechanisms and Therapeutic Perspectives

The dysregulation of Notch signaling is found in many cancers and is closely related to cancer progression. As an important Notch receptor, abnormal Notch4 expression affects several tumor-cell behaviors, including stemness, the epithelial-mesenchymal transition, radio/chemoresistance and angiogenesis. In order to inhibit the oncogenic effects of Notch4 activation, several methods for targeting Notch4 signaling have been proposed. In this review, we summarize the known molecular mechanisms through which Notch4 affects cancer progression. Finally, we discuss potential Notch4-targeting therapeutic strategies as a reference for future research.

The Role of miR-181c in Mechanisms of Diabetes-Impaired Angiogenesis: An Emerging Therapeutic Target for Diabetic Vascular Complications

Diabetes mellitus is estimated to affect up to 700 million people by the year 2045, contributing to an immense health and economic burden. People living with diabetes have a higher risk of developing numerous debilitating vascular complications, leading to an increased need for medical care, a reduced quality of life and increased risk of early death. Current treatments are not satisfactory for many patients who suffer from impaired angiogenesis in response to ischaemia, increasing their risk of ischaemic cardiovascular conditions. These vascular pathologies are characterised by endothelial dysfunction and abnormal angiogenesis, amongst a host of impaired signaling pathways. Therapeutic stimulation of angiogenesis holds promise for the treatment of diabetic vascular complications that stem from impaired ischaemic responses. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis to improve ischaemic complications such as ischaemic heart disease and peripheral artery disease, highlighting the immense unmet need. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis in a clinical setting, highlighting the immense unmet need. MicroRNAs (miRNAs) are emerging as powerful targets for multifaceted diseases including diabetes and cardiovascular disease. This review highlights the potential role of microRNAs as therapeutic targets for rescuing diabetes-impaired angiogenesis, with a specific focus on miR-181c, which we have previously identified as an important angiogenic regulator. Here we summarise the pathways currently known to be regulated by miR-181c, which include the classical angiogenesis pathways that are dysregulated in diabetes, mitochondrial function and axonal guidance, and describe how these relate both directly and indirectly to angiogenesis. The pleiotropic actions of miR-181c across multiple key angiogenic signaling pathways and critical cellular processes highlight its therapeutic potential as a novel target for treating diabetic vascular complications.

Circulating miRNAs as Novel Non-Invasive Biomarkers to Aid the Early Diagnosis of Suspicious Breast Lesions for Which Biopsy Is Recommended

Simple Summary

In population-based screens, tissue biopsy remains the standard practice for women with imaging that suggests breast cancer. We examined circulating microRNAs as minimally invasive diagnostic biomarkers to discriminate malignant from benign breast lesions. A retrospective cohort of plasma samples divided into training and testing sets and a prospective cohort of women with suspicious imaging findings who underwent tissue biopsy were investigated through a global microRNA profile by OpenArray. Seven signatures, involving 5 specific miRNAs (miR-625, miR-423-5p, miR-370-3p, miR-181c, and miR-301b), were identified and validated in the testing set. Among the 7 signatures, the discriminatory performances of 5 of them were confirmed in the prospective cohort.

Abstract

In population-based screens, tissue biopsy remains the standard practice for women with imaging that suggests breast cancer. We examined circulating microRNAs as minimally invasive diagnostic biomarkers to discriminate malignant from benign breast lesions. miRNAs were analyzed by OpenArray in a retrospective cohort of plasma samples including 100 patients with malignant (T), 89 benign disease (B), and 99 healthy donors (HD) divided into training and testing sets and a prospective cohort (BABE) of 289 women with suspicious imaging findings who underwent tissue biopsy. miRNAs associated with disease status were identified by univariate analysis and then combined into signatures by multivariate logistic regression models. By combining 16 miRNAs differentially expressed in the T vs. HD comparison, 26 signatures were also able to significantly discriminate T from B disease. Seven of them, involving 5 specific miRNAs (miR-625, miR-423-5p, miR-370-3p, miR-181c, and miR-301b), were statistically validated in the testing set. Among the 7 signatures, the discriminatory performances of 5 were confirmed in the prospective BABE Cohort. This study identified 5 circulating miRNAs that, properly combined, distinguish malignant from benign breast disease in women with a high likelihood of malignancy.

Epigenetic Regulation of microRNAs in Cancer: Shortening the Distance from Bench to Bedside

Cancer is a complex disease involving alterations of multiple processes, with both genetic and epigenetic features contributing as core factors to the disease. In recent years, it has become evident that non-coding RNAs (ncRNAs), an epigenetic factor, play a key role in the initiation and progression of cancer. MicroRNAs, the most studied non-coding RNAs subtype, are key controllers in a myriad of cellular processes, including proliferation, differentiation, and apoptosis. Furthermore, the expression of miRNAs is controlled, concomitantly, by other epigenetic factors, such as DNA methylation and histone modifications, resulting in aberrant patterns of expression upon the occurrence of cancer. In this sense, aberrant miRNA landscape evaluation has emerged as a promising strategy for cancer management. In this review, we have focused on the regulation (biogenesis, processing, and dysregulation) of miRNAs and their role as modulators of the epigenetic machinery. We have also highlighted their potential clinical value, such as validated diagnostic and prognostic biomarkers, and their relevant role as chromatin modifiers in cancer therapy.

Methylation and Noncoding RNAs in Gastric Cancer: Everything Is Connected

Despite recent progress, gastric cancer remains one of the most common cancers and has a high mortality rate worldwide. Aberrant DNA methylation pattern and deregulation of noncoding RNA expression appear in the early stages of gastric cancer. Numerous investigations have confirmed their significant role in gastric cancer tumorigenesis and their high potential as diagnostic and prognostic biomarkers. Currently, it is clear that these epigenetic regulators do not work alone but interact with each other, generating a complex network. The aim of our review was to summarize the current knowledge of this interaction in gastric cancer and estimate its clinical potential for the diagnosis, prognosis, and treatment of the disease.

The impact of microRNAs on myeloid-derived suppressor cells in cancer

Inflammation promotes cancer development. To a large extent, this can be attributed to the recruitment of myeloid-derived suppressor cells (MDSCs) to tumors. These cells are known for establishing an immunosuppressive tumor microenvironment by suppressing T cell activities. However, MDSCs also promote metastasis and angiogenesis. Critically, as small non-coding RNAs that regulate gene expression, microRNAs (miRNAs) control MDSC activities. In this review, we discuss how miRNA networks regulate key MDSC signaling pathways, how they shape MDSC development, differentiation and activation, and how this impacts tumor development. By targeting the expression of miRNAs in MDSCs, we can alter their main signaling pathways. In turn, this can compromise their ability to promote multiple hallmarks of cancer. Therefore, this may represent a new powerful strategy for cancer immunotherapy.

Adverse Maternal Environment Alters MicroRNA-10b-5p Expression and Its Epigenetic Profile Concurrently with Impaired Hippocampal Neurogenesis in Male Mouse Hippocampus

An adverse maternal environment (AME) predisposes adult offspring toward cognitive impairment in humans and mice. However, the underlying mechanisms remain poorly understood. Epigenetic changes in response to environmental exposure may be critical drivers of this change. Epigenetic regulators, including microRNAs, have been shown to affect cognitive function by altering hippocampal neurogenesis which is regulated in part by brain-derived neurotropic factor (BDNF). We sought to investigate the effects of AME on miR profile and their epigenetic characteristics, as well as neurogenesis and BDNF expression in mouse hippocampus. Using our mouse model of AME which is composed of maternal Western diet and prenatal environmental stress, we found that AME significantly increased hippocampal miR-10b-5p levels. We also found that AME significantly decreased DNA methylation and increased accumulations of active histone marks H3 lysine (K) 4me3, H3K14ac, and -H3K36me3 at miR-10b promoter. Furthermore, AME significantly decreased hippocampal neurogenesis by decreasing cell numbers of Ki67+ (proliferation marker), NeuroD1+ (neuronal differentiation marker), and NeuN+ (mature neuronal marker) in the dentate gyrus (DG) region concurrently with decreased hippocampal BDNF protein levels. We speculate that the changes in epigenetic profile at miR-10b promoter may contribute to upregulation of miR-10b-5p and subsequently lead to decreased BDNF levels in a model of impaired offspring hippocampal neurogenesis and cognition in mice.

Association of miRNA 30c, miRNA 181a and miRNA 570 SNPs with Bladder Cancer Risk in North Indian Population: A Pilot Study

miRNA play role in post transcriptional regulation of genes and serves a range of biological functions such as initiation, development, metastasis etc. which are also hallmarks of cancer. Hence, we evaluated miRNA 181a, miRNA 30c and miRNA 570 in bladder cancer risk association among North Indians. miRNA 570 C/G (rs4143815), miRNA 30c A/G (rs928508) and miRNA 181a C/T (rs12537) single nucleotide polymorphisms (SNPs) were genotyped by allelic discrimination TaqMan assay in 100 bladder cancer (BC) patients and 100 healthy controls. No significant difference was found in the genotype frequencies of the candidate SNPs among cases and controls. However, combined effect of miRNA 570-miRNA 30c (CG + AA) p = 0.005, OR = 0.223, 95% CI and miRNA 570-miRNA 181a (CG + CC) p = 0.003, OR = 0.169, 95% CI conferred association with no risk of BC. miRNA 181a C/T (rs12537), miRNA 30c A/G (rs928508) and miRNA 570 C/G (rs4143815) should be further validated in large sample size to be used as a risk predictor for bladder cancer among North Indians.

MicroRNA Changes in Gastric Carcinogenesis: Differential Dysregulation during Helicobacter pylori and EBV Infection

Despite medical advances, gastric-cancer (GC) mortality remains high in Europe. Bacterial infection with Helicobacter pylori (H. pylori) and viral infection with the Epstein–Barr virus (EBV) are associated with the development of both distal and proximal gastric cancer. Therefore, the detection of these infections and the prediction of further cancer development could be clinically significant. To this end, microRNAs (miRNAs) could serve as promising new tools. MiRNAs are highly conserved noncoding RNAs that play an important role in gene silencing, mainly acting via translational repression and the degradation of mRNA targets. Recent reports demonstrate the downregulation of numerous miRNAs in GC, especially miR-22, miR-145, miR-206, miR-375, and miR-490, and these changes seem to promote cancer-cell invasion and tumor spreading. The dysregulation of miR-106b, miR-146a, miR-155, and the Let-7b/c complex seems to be of particular importance during H. pylori infection or gastric carcinogenesis. In contrast, many reports describe changes in host miRNA expression and outline the effects of bamHI-A region rightward transcript (BART) miRNA in EBV-infected tissue. The differential regulation of these miRNA, acting alone or in close interaction when both infections coexist, may therefore enable us to detect cancer earlier. In this review, we focus on the two different etiologies of gastric cancer and outline the molecular pathways through which H. pylori- or EBV-induced changes might synergistically act via miR-155 dysregulation to potentiate cancer risk. The three markers, namely, H. pylori presence, EBV infection, and miR-155 expression, may be checked in routine biopsies to evaluate the risk of developing gastric cancer.

MiR-181c-5p Mitigates Tumorigenesis in Cervical Squamous Cell Carcinoma via Targeting Glycogen Synthase Kinase 3β Interaction Protein (GSKIP)

Background

Cervical cancer (CC) is a highly prevalent cancer and one of the main causes of death among women worldwide. The miR-181 family has turned out to be associated with tumorigenesis in a variety of tumors by regulating the expression of tumor-related genes. However, the mechanisms and biological function of miR-181c-5p in cervical squamous cell carcinoma (SCC) have not been well elucidated.

Materials and Methods

SiHa cell lines with specific gene overexpression vectors were constructed. Targetscan was used to predict the binding site of miR-181c-5p and GSKIP. MTT assay was used to detect the clone formation rate. Flow cytometry was used to detect the apoptosis rate and to separate the cell markers. The Transwell test was used to detect cell invasion. Immunohistochemistry was used to detect protein expression in tumor tissues. Western Blotting was used to detect the expression levels of related proteins.

Results

GSKIP was predicted to be the target gene of miR-181c-5p in cervical SCC. MiR-181c-5p overexpression suppressed SiHa cells proliferation and promoted apoptosis; the protein expressions of Ki67 and PCNA were decreased, but the expressions of Caspase-3 and Bax/Bcl-2 were increased. The overexpression of miR-181c-5p inhibited the stem-like properties of SiHa cells; the expressions of SOX2, OCT4 and CD44 were decreased. Furthermore, miR-181c-5p upregulation limited the invasion of SiHa cells; the expression of E-cadherin was higher, but the expressions of N-cadherin and Vimentin were lower. MiR-181c-5p overexpression inhibited tumorigenesis in cervical SCC tissues; the expressions of Ki67, Caspase-3, CD44 and Vimentin in vivo were consistent with those in vitro.

Conclusion

Taken together, miR-181c-5p was able to mitigate the cancer cell characteristic and invasive properties of cervical SCC through targeting GSKIP gene.

microRNA-181 serves as a dual-role regulator in the development of human cancers

MicroRNAs (miRNAs) as the regulatory short noncoding RNAs are involved in a wide array of cellular and molecular processes. They negatively regulate gene expression and their dysfunction is correlated with cancer development through modulation of multiple signaling pathways. Therefore, these molecules could be considered as novel biomarkers and therapeutic targets for more effective management of human cancers. Recent studies have demonstrated that the miR-181 family is dysregulated in various tumor tissues and plays a pivotal role in carcinogenesis. They have been shown to act as oncomirs or tumor suppressors considering their mRNA targets and to be involved in cell proliferation, apoptosis, autophagy, angiogenesis and drug resistance. Additionally, these miRNAs have been demonstrated to exert their regulatory effects through modulating multiple signaling pathways including PI3K/AKT, MAPK, TGF-b, Wnt, NF-κB, Notch pathways. Given that, in this review, we briefly summarise the recent studies that have focused on the roles of miRNA-181 family as the multifunctional miRNAs in tumorigenesis and cancer development. These miRNAs may serve as diagnostic and prognostic biomarkers or therapeutic targets in human cancer gene therapy.

MAP Kinases Pathways in Gastric Cancer

Gastric cancer (GC) is turning out today to be one of the most important welfare issues for both Asian and European countries. Indeed, while the vast majority of the disease burden is located in China and in Pacific and East Asia, GC in European countries still account for about 100,000 deaths per year. With this review article, we aim to focus the attention on one of the most complex cellular pathways involved in GC proliferation, invasion, migration, and metastasis: the MAP kinases. Such large kinases family is to date constantly studied, since their discovery more than 30 years ago, due to the important role that it plays in the regulation of physiological and pathological processes. Interactions with other cellular proteins as well as miRNAs and lncRNAs may modulate their expression influencing the cellular biological features. Here, we summarize the most important and recent studies involving MAPK in GC. At the same time, we need to underly that, differently from cancers arising from other tissues, where MAPK pathways seems to be a gold target for anticancer therapies, GC seems to be unique in any aspect. Our aim is to review the current knowledge in MAPK pathways alterations leading to GC, including H. pylori MAPK-triggering to derail from gastric normal epithelium to GC and to encourage researches involved in MAPK signal transduction, that seems to definitely sustain GC development.

Effects of MIR143 on rat sarcoma signaling networks in solid tumors: A brief overview

Rat sarcoma (RAS) is a well-known oncogene that plays important roles in cancer proliferation, cell survival and cell invasion. RAS exists as three major isoforms, Kirsten rat sarcoma (KRAS), Harvey rat sarcoma (HRAS) and neuroblastoma rat sarcoma (NRAS). Mutations of these genes account for approximately 30% of all cancers. Among them, KRAS mutations are the most common, responsible for 85%, followed by NRAS (12%) and HRAS (3%). Although the development of RAS inhibitors has been explored for over the past decade, so far, no effective inhibitor has been found. MicroRNA (miRNA) are a class of small non-coding RNA that control the gene expression of pleural target genes at the post-transcriptional level. MiRNA play critical roles in the physiological and pathological processes at work in cancers, such as cell proliferation, cell death, cell invasion and metastasis. MicroRNA-143 (MIR143) is known to function as a tumor suppressor in a variety of cancers. One of its known mechanisms is suppression of RAS expression and its effector signaling pathways, such as PI3K/AKT and MAPK/ERK. Within the last five years, we developed a potent chemically modified MIR143-3p that enabled us to elucidate the details of the KRAS signaling networks at play in colon and other cancer cells. In this review, we will discuss the role of MIR143-3p in those RAS signaling networks that are related to various biological processes of cancer cells. In addition, we will discuss the possibility of the use of MIR143 as a therapeutic drug for targeting RAS signaling networks.

MicroRNA (miR) dysregulation during Helicobacter pylori-induced gastric inflammation and cancer development: critical importance of miR-155

Dysregulation of noncoding microRNA molecules has been associated with immune cell activation in the context of Helicobacter pylori induced gastric inflammation as well as carcinogenesis, but also with downregulation of mismatch repair genes, and may interfere with immune checkpoint proteins that lead to the overexpression of antigens on gastric tumor cells. Numerous miR-molecules have been described as important tools and markers in gastric inflammation and cancer development -including miR-21, miR-143, miR-145, miR-201, and miR-335- all of which are downregulated in gastric tumors, and involved in cell cycle growth or tumor invasion. Among the many microRNAs involved in gastric inflammation, adenocarcinoma development and immune checkpoint regulation, miR-155 is notable in that its upregulation is considered a key marker of chronic gastric inflammation that predisposes a patient to gastric carcinogenesis. Among various other miRs, miR-155 is highly expressed in activated B and T cells and in monocytes/macrophages present in chronic gastric inflammation. Notably, miR-155 was shown to downregulate the expression of certain MMR genes, such as MLH1, MSH2, and MSH6. In tumor-infiltrating miR-155-deficient CD8⁺ T cells, antibodies against immune checkpoint proteins restored the expression of several derepressed miR-155 targets, suggesting that miR-155 may regulate overlapping pathways to promote antitumor immunity. It may thus be of high clinical impact that gastric pathologies mediated by miR-155 result from its overexpression. This suggests that it may be possible to therapeutically attenuate miR-155 levels for gastric cancer treatment and/or to prevent the progression of chronic gastric inflammation into cancer.

The Importance of microRNAs in RAS Oncogenic Activation in Human Cancer

microRNAs (miRNAs) regulate gene expression by modulating the translation of protein-coding RNAs. Their aberrant expression is involved in various human diseases, including cancer. Here, we summarize the experimental pieces of evidence that proved how dysregulated miRNA expression can lead to RAS (HRAS, KRAS, or NRAS) activation irrespective of their oncogenic mutations. These findings revealed relevant pathogenic mechanisms as well as mechanisms of resistance to target therapies. Based on this knowledge, potential approaches for the control of RAS oncogenic activation can be envisioned.

NOTCH signaling pathway and non-coding RNAs in cancer

Malignant tumors, known as cancer, seriously threaten human life and health. Cancer has the characteristics of abnormal cell differentiation, proliferation, invasion and metastasis. As a result, cancer often accompanied by poor prognosis and a lower survival rate. Notch signaling pathway is a highly conserved system in many multicellular organisms, and which has been proved to play a biological role in many cancers. In recent years, increasing evidence has shown that non-coding RNA can not only activate or inhibit NOTCH pathway, but also regulate the occurrence and development of cancer through NOTCH pathway. Therefore, we focus on the cancer-NOTCH-non-coding RNA axis in this review, and provide new ideas for cancer therapy.

Identification of microRNAs modulated by DNA hypomethylating drugs in extranodal NK/T-cell lymphoma

To identify epigenetically silenced miRNAs and to investigate their influences on predictive target oncogenes in extranodal natural killer/T-cell lymphoma (NKTCL). Decitabine treatment was performed to evaluate methylated miRNAs in NKTCL cells. The relationship between a given miRNA and its target mRNA was validated using 24 tumor tissues. miR-379, miR-134, miR-20b, miR-376a, miR-654-3p, miR-143, miR-181c, miR-1225-5p, miR-1246, and miR-1275 were epigenetically silenced in SNK6 cells. miR-134, miR-376a, miR-143 and miR-181c significantly affected cellular viability. PDGFRα was regulated by miR-34a and miR-181c. miR-143, miR-20b and miR34a regulated STAT3 expression. miR-20b and miR-143 expression showed inverse correlations with STAT3 mRNA expression in NKTCL tissues. K-RAS was regulated by miR-181c. Downregulation of cell viability by salirasib treatment was identified. miRNAs were downregulated by DNA methylation, and several microRNAs affected the viability of NKTCL cells. miR-34a and miR-181c may be involved in the oncogenic progression of NKTCL through the regulation of PDGFRα, STAT3, and K-RAS.

The secret messages between mitochondria and nucleus in muscle cell biology

Over two thousand proteins are found in the mitochondrial compartment but the mitochondrial genome codes for only 13 proteins. The majority of mitochondrial proteins are products of nuclear genes and are synthesized in the cytosol, then translocated into the mitochondria. Most of the subunits of the five respiratory chain complexes in the inner mitochondrial membrane, which generate a proton gradient across the membrane and produce ATP, are encoded by nuclear genes. Therefore, it is quite clear that import of nuclear-encoded proteins into the mitochondria is essential for mitochondrial function. Nuclear to mitochondrial communication is well studied. However, there is another arm to this communication, mitochondria to nucleus retrograde signaling. This plays an important role in the maintenance of cellular homeostasis, and is less well studied. Several transcription factors, including Sp1, SIRT3 and GSP2, are activated by altered mitochondrial function. These activated transcription factors then translocate to the nucleus. Based on the mitochondrially generated molecular signal, nuclear genes are targeted, which alters transcription of nuclear genes that code for mitochondrial proteins. This review article will mainly focus on this interactive and bi-directional communication between mitochondria and nucleus, and how this communication plays a significant role in muscle cell biology.

DNA methylation-regulated and tumor-suppressive roles of miR-487b in colorectal cancer via targeting MYC, SUZ12, and KRAS

Human colorectal cancer (CRC), characterized by its high morbidity and lethality, seriously threatens human health and lives. MicroRNA‐487b (miR‐487b) is currently reported to be aberrantly expressed in several tumors, but the detailed functions and underlying mechanisms of miR‐487b in CRC remain unclear. Here, we found that miR‐487b is downregulated in CRC cell lines and is markedly decreased in tumor specimens derived from CRC patients. MiR‐487b inhibits cell proliferation, migration and invasion and promotes the apoptosis of CRC cells in vitro. Statistical analysis of clinical samples indicates that miR‐487b may serve as a biomarker for early CRC diagnosis. Inverse correlations between the expression levels of MYC, SUZ12, and KRAS and that of miR‐487b exist in vitro and in CRC patient tissue specimens. Further experiments demonstrated the regulatory effects of miR‐487b on MYC, SUZ12, and KRAS, and the disruption of these genes partially restores the miR‐487b inhibitor‐induced phenotype. Additionally, miR‐487b promoter region is in a DNA hypermethylated condition and the DNA methyltransferase inhibitor 5‐aza‐2’‐deoxycytidine (5‐Aza) increases the levels of miR‐487b but suppresses the expression of MYC, SUZ12, and KRAS in a time‐ and concentration‐dependent manner in CRC cells. Collectively, miR‐487b is regulated by DNA methylation and it functions as a tumor suppressor in CRC mainly through targeting MYC, SUZ12, and KRAS. Our study provides insight into the regulatory network in CRC cells, offering a new target for treating CRC patients.

Up-Regulation of MiR-1915 Inhibits Proliferation, Invasion, and Migration of Helicobacter pylori-Infected Gastric Cancer Cells via Targeting RAGE

PURPOSE

Helicobacter pylori (HP)-infected gastric cancer (GC) is known to be a fatal malignant tumor, but the molecular mechanisms underlying its proliferation, invasion, and migration remain far from being completely understood. Our aim in this study was to explore miR-1915 expression and its molecular mechanisms in regulating proliferation, invasion, and migration of HP-infected GC cells.

MATERIALS AND METHODS

Quantitative real-time PCR and western blot analysis were performed to determine miR-1915 and receptor for advanced glycation end product (RAGE) expression in HP-infected GC tissues and gastritis tissues, as well as human gastric mucosal cell line GES-1 and human GC cell lines SGC-7901 and MKN45. CCK8 assay and transwell assay were performed to detect the proliferation, invasion, and migration capabilities. MiR-1915 mimics and miR-1915 inhibitor were transfected into GC cells to determine the target relationship between miR-1915 and RAGE.

RESULTS

MiR-1915 was under-expressed, while RAGE was over-expressed in HP-infected GC tissues and GC cells. Over-expressed miR-1915 could attenuate cellular proliferation, invasion, and migration capacities. RAGE was confirmed to be the target gene of miR-1915 by bioinformatics analysis and luciferase reporter assay. Moreover, HP-infected GC cellular proliferation, invasion, and migration were inhibited after treatment with pcDNA-RAGE.

CONCLUSION

MiR-1915 exerted tumor-suppressive effects on cellular proliferation, invasion, and migration of HP-infected GC cells via targeting RAGE, which provided an innovative target candidate for treatment of HP-infected GC.

Decreased MicroRNA miR-181c Expression Associated with Gastric Cancer

PURPOSE

This study investigated miRNA-181c expression in control patients (healthy gastric mucosa), patients with gastritis, and patients with gastric cancer. The presence of Helicobacter pylori was determined, and the associations between H. pylori infection, levels of miRNA-181c expression, and gastric disease were also analyzed.

METHODS

A total of 158 subjects were included in the study, and the three groups were respectively composed of 53 controls, 86 patients with gastritis, and 19 patients with gastric cancer. miRNA-181c expression and H. pylori infection were determined by quantitative real-time PCR and PCR, respectively. The subsequent target gene analysis was performed using the bioinformatics approach to understand the possible mechanisms of gastric cancer.

RESULTS

We determined significantly lower miRNA-181c expression in the gastric cancer group when compared to the control and gastritis groups, regardless of the presence of H. pylori. There was no difference in miRNA-181c expression between the control group and gastritis group, whether the presence of H. pylori was considered or not. The bioinformatics approach identified several genes as possible targets for miRNA-181c, including the X-linked inhibitor of apoptosis (XIAP) gene (which encodes a protein that belongs to a family of apoptotic suppressor proteins), the caspase 9 gene, and the caspase 3 gene. All target genes identified may be involved in gastric cancer and apoptosis pathways.

CONCLUSION

The results suggest that the presence of H. pylori has no influence on microRNA expression and that the downregulation of miR-181c may play an important role in gastric cancer progression by controlling important genes associated with apoptosis. Therefore, miRNA-181c may be a potential marker of gastric cancer.

Proposed Molecular and miRNA Classification of Gastric Cancer

Gastric cancer (GC) is a common malignant neoplasm worldwide and one of the main cause of cancer-related deaths. Despite some advances in therapies, long-term survival of patients with advanced disease remains poor. Different types of classification have been used to stratify patients with GC for shaping prognosis and treatment planning. Based on new knowledge of molecular pathways associated with different aspect of GC, new pathogenetic classifications for GC have been and continue to be proposed. These novel classifications create a new paradigm in the definition of cancer biology and allow the identification of relevant GC genomic subsets by using different techniques such as genomic screenings, functional studies and molecular or epigenetic characterization. An improved prognostic classification for GC is essential for the development of a proper therapy for a proper patient population. The aim of this review is to discuss the state-of-the-art on combining histological and molecular classifications of GC to give an overview of the emerging therapeutic possibilities connected to the latest discoveries regarding GC.

MicroRNA181c inhibits prostate cancer cell growth and invasion by targeting multiple ERK signaling pathway components

BACKGROUND

The ERK signaling pathway is frequently deregulated in tumorigenesis, mostly by classical mechanisms such as gene mutation of its components (eg, RAS and RAF). However, whether and how multiple key components of ERK pathway are regulated by microRNAs are not clear.

METHODS

We firstly predicted post-transcriptional regulation of multiple key components of the ERK signaling pathway by miR181c through bioinformatics analysis, and then confirmed the post-transcriptional regulation by dual luciferase reporter gene assays and Western blot analysis. The biological effects of miR181c on prostate cancer cell proliferation, apoptosis, migration, and invasion were measured by CCK-8 assay, flow cytometry, wound scratch assay, transwell cell migration, and invasion assays.

RESULTS

miR181c post-transcriptionally regulated multiple key members of the ERK signaling pathway, including extracellular signal-regulated kinase 2 (ERK2), ribosomal S6 kinase 2 (RSK2), serum response factor (SRF), and FBJ murine osteosarcoma viral oncogene homolog (c-Fos). Ectopic expression of miR181c mimics effectively suppressed prostate cancer cell proliferation, migration, and invasion, but promoted cell apoptosis. Furthermore, miR181c treatment combined with the multi-kinase inhibitor sorafenib significantly enhanced these anti-tumor effects.

CONCLUSIONS

Downregulation of miR181c results in deregulated ERK signaling and promotes prostate cancer cell growth and metastasis.

Altered expression of miRNAs and methylation of their promoters are correlated in neuroblastoma

Neuroblastoma is the most common human extracranial solid tumor during infancy. Involvement of several miRNAs in its pathogenesis has been ascertained. Interestingly, most of their encoding genes reside in hypermethylated genomic regions: thus, their tumor suppressor function is normally disallowed in these tumors. To date, the therapeutic role of the demethylating agent 5′-Aza-2 deoxycytidine (5'-AZA) and its effects on miRNAome modulation in neuroblastoma have not been satisfactorily explored. Starting from a high-throughput expression profiling of 754 miRNAs and based on a proper selection, we focused on miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p as candidate miRNAs for our analysis. They resulted downregulated in four neuroblastoma cell lines with respect to normal adrenal gland. MiRNAs 29a-3p and 34b-3p also resulted downregulated in vivo in a murine neuroblastoma progression model. Unlike the amount of methylation of their encoding gene promoters, all these miRNAs were significantly overexpressed following treatment with 5′-AZA. Transfection with candidate miRNAs mimics significantly decreased neuroblastoma cells proliferation rate. A lower expression of miR-181c was significantly associated to a worse overall survival in a public dataset of 498 neuroblastoma samples (http://r2.amc.nl). Our data strongly suggest that CDK6, DNMT3A, DNMT3B are targets of miR-29a-3p, while CCNE2 and E2F3 are targets of miR-34b-3p. Based on all these data, we propose that miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p are disallowed tumor suppressor genes in neuroblastoma and suggest them as new therapeutic targets in neuroblastoma.

Epigenetics and MicroRNAs in Cancer

The ability to reprogram the transcriptional circuitry by remodeling the three-dimensional structure of the genome is exploited by cancer cells to promote tumorigenesis. This reprogramming occurs because of hereditable chromatin chemical modifications and the consequent formation of RNA-protein-DNA complexes that represent the principal actors of the epigenetic phenomena. In this regard, the deregulation of a transcribed non-coding RNA may be both cause and consequence of a cancer-related epigenetic alteration. This review summarizes recent findings that implicate microRNAs in the aberrant epigenetic regulation of cancer cells.

RAS-MAPK pathway epigenetic activation in cancer: miRNAs in action

The highly conserved RAS-mitogen activated protein kinase (MAPK) signaling pathway is involved in a wide range of cellular processes including differentiation, proliferation, and survival. Somatic mutations in genes encoding RAS-MAPK components frequently occur in many tumors, making the RAS-MAPK a critical pathway in human cancer. Since the pioneering study reporting that let-7 miRNA acted as tumor suppressor by repressing the RAS oncogene, growing evidence has suggested the importance of miRNAs targeting the RAS-MAPK in oncogenesis. MiRNAs alterations in human cancers may act as a rheostat of the oncogenic RAS signal that is often amplified as cancers progress. However, specific mechanisms leading to miRNAs deregulation and their functional consequences in cancer are far from being fully elucidated. In this review, we provide an experimental-validated map of RAS-MAPK oncomiRs and tumor suppressor miRNAs from transmembrane receptor to downstream ERK proteins. MiRNAs could be further considered as potential genetic biomarkers for diagnosis, prognosis, or therapeutic purpose.

Loss of miR-107, miR-181c and miR-29a-3p Promote Activation of Notch2 Signaling in Pediatric High-Grade Gliomas (pHGGs)

The mechanisms by which microRNAs control pediatric high-grade gliomas (pHGGs) have yet to be fully elucidated. Our studies of patient-derived pHGG tissues and of the pHGG cell line KNS42 revealed down-regulation in these tumors of three microRNAs, specifically miR-107, miR-181c, and miR-29a-3p. This down-regulation increases the proliferation of KNS42 cells by de-repressing expression of the Notch2 receptor (Notch2), a validated target of miR-107 and miR-181c and a putative target of miR-29a-3p. Inhibition (either pharmacologic or genetic) of Notch2 or re-expression of the implicated microRNAs (all three combined but also individually) significantly reduced KNS42 cell proliferation. These findings suggest that Notch2 pathway activation plays a critical role in pHGGs growth and reveal a direct epigenetic mechanism that controls Notch2 expression, which could potentially be targeted by novel forms of therapy for these childhood tumors characterized by high-morbidity and high-mortality.

Dysregulation of miR-181c expression influences recurrence of endometrial endometrioid adenocarcinoma by modulating NOTCH2 expression: An NRG Oncology/Gynecologic Oncology Group study

OBJECTIVE

Endometrial cancer can be diagnosed early and cured, yet cases that recur portend a very poor prognosis with over 10,000 women succumbing to the disease every year. In this study we addressed the question of how to recognize cases likely to recur early in the course of therapy using dysregulation of tumor microRNAs (miRNAs) as predictors.

METHODS

Using the tissue collection from Gynecologic Oncology Group Study-210, we selected and analyzed expression of miRNAs in 54 recurrent and non-recurrent cases. The three most common histologic types, endometrioid adenocarcinoma (EEA), serous adenocarcinoma (ESA) and carcinosarcoma (UCS), were analyzed as three independent sets and their miRNA expression profiles compared.

RESULTS

Only one miRNA was statistically different between recurrent and non-recurrent cases, and in only one histologic type: significant down-regulation of miR-181c was observed in EEA recurrence. Using several well-known databases to assess miR-181c targets, one target of particular relevance to cancer, NOTCH2, was well supported. Using The Cancer Genome Atlas and our validation tumor panel from the GOG-210 cohort, we confirmed that NOTCH2 is significantly over-expressed in EEA. In the most relevant endometrial adenocarcinoma cell model, Ishikawa H, altering miR-181c expression produces significant changes in NOTCH2 expression, consistent with direct targeting.

CONCLUSIONS

Our findings suggest that increased NOTCH2 via loss of miR-181c is a significant component of EEA recurrence. This presents an opportunity to develop miR-181c and NOTCH2 as markers for early identification of high risk cases and the use of NOTCH inhibitors in the prevention or treatment of recurrent disease.

Crosstalk between the Notch signaling pathway and non-coding RNAs in gastrointestinal cancers

The Notch signaling pathway is one of the main signaling pathways that mediates direct contact between cells, and is essential for normal development. It regulates various cellular processes, including cell proliferation, apoptosis, migration, invasion, angiogenesis and metastasis. It additionally serves an important function in tumor progression. Non-coding RNAs mainly include small microRNAs, long non-coding RNAs and circular RNAs. At present, a large body of literature supports the biological significance of non-coding RNAs in tumor progression. It is also becoming increasingly evident that cross-talk exists between Notch signaling and non-coding RNAs. The present review summarizes the current knowledge of Notch-mediated gastrointestinal cancer cell processes, and the effect of the crosstalk between the three major types of non-coding RNAs and the Notch signaling pathway on the fate of gastrointestinal cancer cells.

The role of Notch signaling in gastric carcinoma: molecular pathogenesis and novel therapeutic targets

Notch signaling, an evolutionarily conserved signaling cascade system, is involved in promoting the progression of different types of cancers. Within the past decades, the Notch signaling pathway has increasingly been shown to have a primary role in deciding the fate of cancer cells and cancer stem cells in the stomach. Most components of Notch signaling are strongly expressed at different levels in gastric carcinoma tissue samples and are associated with a considerable number of clinical parameters. Moreover, crosstalk signaling between the Notch pathway and the Wnt, Ras, and NF-κB pathways promotes the process of gastric carcinogenesis. Consequently, this increases proliferation and prevents apoptosis in gastric cancer cells, and it contributes to the induction of angiogenesis and accelerates the progression of the epithelial-to-mesenchymal transition. Although the Notch signaling pathway presents novel therapeutic targets for cancer therapeutic intervention, there is still a dearth of in-depth understanding of the molecular mechanisms of Notch signaling in gastric carcinoma. In this review, we summarize the landscape of the Notch signaling pathway and recent findings on Notch signaling in gastric cancer. Furthermore, advanced studies and clinical treatments targeting the Notch signaling pathway arediscussed.

A unified model of the hierarchical and stochastic theories of gastric cancer

Gastric cancer (GC) is a life-threatening disease worldwide. Despite remarkable advances in treatments for GC, it is still fatal to many patients due to cancer progression, recurrence and metastasis. Regarding the development of novel therapeutic techniques, many studies have focused on the biological mechanisms that initiate tumours and cause treatment resistance. Tumours have traditionally been considered to result from somatic mutations, either via clonal evolution or through a stochastic model. However, emerging evidence has characterised tumours using a hierarchical organisational structure, with cancer stem cells (CSCs) at the apex. Both stochastic and hierarchical models are reasonable systems that have been hypothesised to describe tumour heterogeneity. Although each model alone inadequately explains tumour diversity, the two models can be integrated to provide a more comprehensive explanation. In this review, we discuss existing evidence supporting a unified model of gastric CSCs, including the regulatory mechanisms of this unified model in addition to the current status of stemness-related targeted therapy in GC patients.

Hypoxia-induced miR-210 promoter demethylation enhances proliferation, autophagy and angiogenesis of schwannoma cells

Hypoxia, a dominant feature in cancer occurrence and evolution, exists throughout the progression of most malignant tumors. This study focused on the mechanism of hypoxia-induced miR-210 upregulation, and the miR-210 functions in schwannoma. We detected microvascular density, vascular endothelial growth factor (VEGF) and miR-210 expression levels using schwannoma tissue mciroarray. The results showed that miR-210 expression was significantly associated with VEGF. Moreover, the cytological tests showed that hypoxia induced miR-210 expression, while reduce ephrin-A3 expression. The bisulfate genomic sequencing PCR results showed that miR-210 promoter region was hypermethylated in RT4-D6P2T in normoxia, while demethylated in hypoxia, and the region included the hypoxia-inducible factor-1α (HIF-1α) response element site. Cellular function research showed that hypoxia resulted in RT4-D6P2T apoptosis, higher autophage and invasion. Besides, hypoxia can affect HIF-1α/VEGF-mediated angiogenesis. To learn about the specific functions of miR-210, we found that with miR-210 inhibition, tumor cell apoptosis increased, autophagy and angiogenesis reduced, and the cell cycle was arrested. Hypoxia promoted miR-210 expression through promoter demethylation, then consequently enhanced tumor cell proliferation and autophagy, increasing tumor cell angiogenesis. Thus, miR-210 could be a potential marker for judging tumor malignancy and be taken as an effective target for clinical auxiliary treatment of neurilemmoma.

MicroRNAs and Epigenetics

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression mainly at the posttranscriptional level. Similar to protein-coding genes, their expression is also controlled by genetic and epigenetic mechanisms. Disruption of these control processes leads to abnormal expression of miRNAs in cancer. In this chapter, we discuss the supportive links between miRNAs and epigenetics in the context of carcinogenesis. miRNAs can be epigenetically regulated by DNA methylation and/or specific histone modifications. However, they can themselves (epi-miRNAs) repress key enzymes that drive epigenetic remodeling and also bind to complementary sequences in gene promoters, recruiting specific protein complexes that modulate chromatin structure and gene expression. All these issues affect the transcriptional landscape of cells. Most important, in the cancer clinical scenario, knowledge about miRNAs epigenetic dysregulation can not only be beneficial as a prognostic biomarker, but can also help in the design of new therapeutic approaches.

MicroRNAs in Oncogenesis and Tumor Suppression

MicroRNAs (MiRNAs) have emerged in the last 15 years as central players in the biology of cancer. Increasing lines of evidence have supported their regulatory role in the expression of both oncogenes and tumor-suppressor genes, progressively clarifying which genes are modulated by specific MiRNAs dysregulated in cancer. Intriguingly, a "target-specific" understanding of MiRNA function in oncology has been replaced by a more "pathway-specific" vision of their involvement in cancer biology. This work provides a state-of-the-art knowledge of the role of MiRNAs in the most frequently altered signaling pathways in cancer cells and provides an updated overview on some of the most relevant findings trying to decode the complex molecular mechanisms of cancer.

MicroRNA-149 is epigenetically silenced tumor-suppressive microRNA, involved in cell proliferation and downregulation of AKT1 and cyclin D1 in human glioblastoma multiforme

Aberrant DNA methylation has been shown to inactivate tumor suppressor genes during carcinogenesis. MicroRNA-149 (miR-149) was recently demonstrated to function as a tumor suppressor gene in glioblastoma multiforme (GBM). However, the potential linkage of miR-149 levels and the underlying epigenetic regulatory mechanism in human GBM has not been studied. We used quantitative real-time polymerase chain reaction to investigate the levels of miR-149 in GBM tissues, their matched adjacent normal tissues, and glioblastoma U87MG cell line. Using bisulfite genomic sequencing technology, DNA methylation status of upstream region of miR-149 was evaluated in study population groups and the U87MG cell line. After treatment of cells with 5-aza-2′-deoxycitidine (5-aza-dC), the DNA methylation status, gene expression, and target protein levels of miR-149 were investigated. Our studies revealed that methylation and expression levels of miR-149 were significantly increased and decreased, respectively in GBM patients relative to the adjacent normal tissues (P < 0.01). MiR-149 suppressed the expression of AKT1 and cyclin D1 and reduced the proliferative activities of the U87MG cell line. Treatment of U87MG cells with 5-aza-dC reversed the hypermethylation status of miR-149, enhanced the expression of its gene, and decreased target mRNA and proteins levels (P < 0.01). These findings suggest that the methylation mechanism is associated with decreased expression levels of miR-149, which may in turn lead to the increased levels of its oncogenic target proteins.

Iodine-125 irradiation inhibits invasion of gastric cancer cells by reactivating microRNA-181c expression

Iodine-125 (¹²⁵I) seed implantation has been widely used for the treatment of unresectable advanced tumors. However, the molecular mechanisms underlying the tumor-suppressive effects of ¹²⁵I irradiation have not been fully elucidated. The present study demonstrated that ¹²⁵I irradiation suppresses cell viability and inhibits cell invasiveness of gastric cancer KATO-III and MKN45 cells. Further mechanistic analysis suggested the involvement of microRNA (miR)-181c in the inhibitory effects induced by ¹²⁵I irradiation. Methylated DNA immunoprecipitation coupled with quantitative-polymerase chain reaction demonstrated that treatment with ¹²⁵I irradiation, at the dose of 4 Gy, induced promoter demethylation of the miR-181c gene in KATO-III and MKN45 cells. Following irradiation, the expression of miR-181c was significantly increased, which may be attributed to the demethylation caused by ¹²⁵I irradiation. In addition, upregulation of miR-181c by administration of miR-181c mimics decreased cell invasion, suggesting the role of miR-181c as a tumor suppressor. More importantly, the tumor-suppressive effects of ¹²⁵I irradiation were significantly compromised by the introduction of miR-181c inhibitors. Overall, these results reveal that ¹²⁵I irradiation inhibits invasiveness of gastric cancer cells by reactivating miR-181c at the epigenetic level, thereby providing important molecular evidence for the anticancer effects of ¹²⁵I irradiation.

Potential Diagnostic, Prognostic and Therapeutic Targets of MicroRNAs in Human Gastric Cancer

Human gastric cancer (GC) is characterized by a high incidence and mortality rate, largely because it is normally not identified until a relatively advanced stage owing to a lack of early diagnostic biomarkers. Gastroscopy with biopsy is the routine method for screening, and gastrectomy is the major therapeutic strategy for GC. However, in more than 30% of GC surgical patients, cancer has progressed too far for effective medical resection. Thus, useful biomarkers for early screening or detection of GC are essential for improving patients’ survival rate. MicroRNAs (miRNAs) play an important role in tumorigenesis. They contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors. Because of their stability in tissues, serum/plasma and other body fluids, miRNAs have been suggested as novel tumor biomarkers with suitable clinical potential. Recently, aberrantly expressed miRNAs have been identified and tested for clinical application in the management of GC. Aberrant miRNA expression profiles determined with miRNA microarrays, quantitative reverse transcription-polymerase chain reaction and next-generation sequencing approaches could be used to establish sample specificity and to identify tumor type. Here, we provide an up-to-date summary of tissue-based GC-associated miRNAs, describing their involvement and that of their downstream targets in tumorigenic and biological processes. We examine correlations among significant clinical parameters and prognostic indicators, and discuss recurrence monitoring and therapeutic options in GC. We also review plasma/serum-based, GC-associated, circulating miRNAs and their clinical applications, focusing especially on early diagnosis. By providing insights into the mechanisms of miRNA-related tumor progression, this review will hopefully aid in the identification of novel potential therapeutic targets.

Cullin-5, a ubiquitin ligase scaffold protein, is significantly underexpressed in endometrial adenocarcinomas and is a target of miR-182

Altered expression of cullin-5 (CUL5), a member of the cullin-RING E3 ubiquitin ligase family, has been implicated in a number of types of cancers including breast, cervical and hepatocellular cancers. In the present study, we found that CUL5 expression was significantly decreased in both endometrioid and serous endometrial adenocarcinomas with the more aggressive serous type displaying a higher reduction (−4.3-fold) than the less aggressive endometrioid type (−2.9-fold). Overexpression of CUL5 mRNA and protein in Ishikawa H endometrial cancer cells resulted in decreased cell proliferation and in a reduction in CUL5-RING E3 ligase downstream clients JAK2 and FAS-L. Finally, we demonstrated for the first time that CUL5 is a direct target of miR-182 that we previously showed to be significantly overexpressed in endometrial adenocarcinomas and we provided evidence that increased miR-182 expression is, at least in part, a result of demethylation of its upstream promoter. These data suggest a cascade in which miR-182 expression is epigenetically increased leading to decreased CUL5 expression and increased cellular proliferation. The final step in the cascade may be operating through a decrease in ubiquitination of pro-growth CUL5 ubiquitin ligase clients. This cascade offers a series of potential interventional steps involving epigenetic modification, miRNA and/or gene targeting and ubiquitination.

Comparison of Prognostic MicroRNA Biomarkers in Blood and Tissues for Gastric Cancer

Gastric cancer (GC) still keeps up high mortality worldwide with poor prognosis. Efficient and non-invasive prognostic biomarkers are urgently needed. MicroRNAs are non-coding RNAs playing roles in post-transcriptional gene regulation, which contribute to various biological processes such as development, differentiation and carcinogenesis. MicroRNA expression profiles have been associated with the prognosis and outcome in GC. MicroRNA prognostic biomarkers have been identified from blood or tissues samples, but with different prognostic features. Understanding the various roles of microRNAs in different sample sources of GC will provide deep insights into GC progression. In this review, we highlight the distinct prognostic roles of microRNAs biomarkers in blood and tissue according to their relationships with prognostic parameters, survival rates and target pathways. This will be useful for non-invasive biomarker development and selection in prognosis of GC.

MicroRNA Methylation in Colorectal Cancer

Epigenetic alterations such as DNA methylation, histone modifications and non-coding RNA (including microRNA) associated gene silencing have been identified as a major characteristic in human cancers. These alterations may occur more frequently than genetic mutations and play a key role in silencing tumor suppressor genes or activating oncogenes, thereby affecting multiple cellular processes. In recent years, studies have shown that microRNAs, that act as posttranscriptional regulators of gene expression are frequently deregulated in colorectal cancer (CRC), via aberrant DNA methylation. Over the past decade, technological advances have revolutionized the field of epigenetics and have led to the identification of numerous epigenetically dysregulated miRNAs in CRC, which are regulated by CpG island hypermethylation and DNA hypomethylation. In addition, aberrant DNA methylation of miRNA genes holds a great promise in several clinical applications such as biomarkers for early screening, prognosis, and therapeutic applications in CRC.

MicroRNA-181c inhibits glioblastoma cell invasion, migration and mesenchymal transition by targeting TGF-β pathway

MicroRNAs (miRNAs) are small non-coding RNAs frequently dysregulated in human malignancies. In this study, we found that miR-181c was down-regulated both in glioblastoma tissues and cell lines. We also annotated 566 TCGA miRNA expression profiles and found that patients with high microRNA-181c (miR-181c)-expressing tumors had significantly longer OS and PFS. Overexpression of miR-181c evidently inhibited glioblastoma cell line T98G migration and invasion. Further, the expression of E-cadherin was significantly upregulated and that of N-cadherin and vimentin was significantly down-regulated. We also found that miR-181c overexpression inhibited TGF-β signaling by down-regulating TGFBR1, TGFBR2 and TGFBRAP1 expression. Overall, our study found that miR-181c plays a key role in glioblastoma cell invasion, migration and mesenchymal transition suggesting potential therapeutic applications.