MicroRNA-7 functions as an anti-metastatic microRNA in gastric cancer by targeting insulin-like growth factor-1 receptor

STR mutations on chromosome 15q cause thyrotropin resistance by activating a primate-specific enhancer of MIR7-2/MIR1179

Thyrotropin (TSH) is the master regulator of thyroid gland growth and function. Resistance to TSH (RTSH) describes conditions with reduced sensitivity to TSH. Dominantly inherited RTSH has been linked to a locus on chromosome 15q, but its genetic basis has remained elusive. Here we show that non-coding mutations in a (TTTG)4 short tandem repeat (STR) underlie dominantly inherited RTSH in all 82 affected participants from 12 unrelated families. The STR is contained in a primate-specific Alu retrotransposon with thyroid-specific cis-regulatory chromatin features. Fiber-seq and RNA-seq studies revealed that the mutant STR activates a thyroid-specific enhancer cluster, leading to haplotype-specific upregulation of the bicistronic MIR7-2/MIR1179 locus 35 kb downstream and overexpression of its microRNA products in the participants' thyrocytes. An imbalance in signaling pathways targeted by these micro-RNAs provides a working model for this cause of RTSH. This finding broadens our current knowledge of genetic defects altering pituitary-thyroid feedback regulation.

Non-coding RNAs as potential therapeutic targets for receptor tyrosine kinase signaling in solid tumors: current status and future directions

This review article presents an in-depth analysis of the current state of research on receptor tyrosine kinase regulatory non-coding RNAs (RTK-RNAs) in solid tumors. RTK-RNAs belong to a class of non-coding RNAs (nc-RNAs) responsible for regulating the expression and activity of receptor tyrosine kinases (RTKs), which play a critical role in cancer development and progression. The article explores the molecular mechanisms through which RTK-RNAs modulate RTK signaling pathways and highlights recent advancements in the field. This include the identification of potential new RTK-RNAs and development of therapeutic strategies targeting RTK-RNAs. While the review discusses promising results from a variety of studies, encompassing in vitro, in vivo, and clinical investigations, it is important to acknowledge the challenges and limitations associated with targeting RTK-RNAs for therapeutic applications. Further studies involving various cancer cell lines, animal models, and ultimately, patients are necessary to validate the efficacy of targeting RTK-RNAs. The specificity of ncRNAs in targeting cellular pathways grants them tremendous potential, but careful consideration is required to minimize off-target effects, the article additionally discusses the potential clinical applications of RTK-RNAs as biomarkers for cancer diagnosis, prognosis, and treatment. In essence, by providing a comprehensive overview of the current understanding of RTK-RNAs in solid tumors, this review emphasizes their potential as therapeutic targets for cancer while acknowledging the associated challenges and limitations.

Identification of multiple organ metastasis-associated hub mRNA/miRNA signatures in non-small cell lung cancer

Metastasis remains major cause of treatment failure in non-small cell lung cancer (NSCLC). A comprehensive characterization of the transcriptomic landscape of NSCLC-cells with organ-specific metastatic potentials would advance our understanding of NSCLC metastasis process. In this study, we established NSCLC bone-metastatic (BoM), brain-metastatic (BrM), and lymph-metastatic (LnM) cells by an in vivo spontaneous metastatic model. Subsequently, by analyzing the entire transcriptomic profiles of BoM, BrM, LnM, LuM, in comparison with their parental cell line L9981, we identified miR-660-5p as a key driver that is associated with NSCLC progression and distant metastasis, potentially through its targeting of LIMCH1, SMARCA5 and TPP2. In addition, a six-gene signature (ADRB2, DPYSL2, IL7R, LIMCH1, PIK3R1, and SOX2) was subsequently established to predict NSCLC metastasis based on differentially expressed genes, three of which (DPYSL2, PIK3R1, LIMCH1) along with the transcriptional factors RB1 and TP63, were ultimately validated by experiments. Taken together, aberrant gene signature and miRNA can serve as biomarkers for predicting NSCLC distant metastasis, and targeting them could potentially contribute to the development of novel therapeutic strategies.

The Role of microRNAs in Inflammation

Inflammation is a biological response of the immune system to various insults, such as pathogens, toxic compounds, damaged cells, and radiation. The complex network of pro- and anti-inflammatory factors and their direction towards inflammation often leads to the development and progression of various inflammation-associated diseases. The role of small non-coding RNAs (small ncRNAs) in inflammation has gained much attention in the past two decades for their regulation of inflammatory gene expression at multiple levels and their potential to serve as biomarkers and therapeutic targets in various diseases. One group of small ncRNAs, microRNAs (miRNAs), has become a key regulator in various inflammatory disease conditions. Their fine-tuning of target gene regulation often turns out to be an important factor in controlling aberrant inflammatory reactions in the system. This review summarizes the biogenesis of miRNA and the mechanisms of miRNA-mediated gene regulation. The review also briefly discusses various pro- and anti-inflammatory miRNAs, their targets and functions, and provides a detailed discussion on the role of miR-10a in inflammation.

Hsa-microRNA-370-3p targeting Snail and Twist1 suppresses IL-8/STAT3-driven hepatocellular carcinoma metastasis

The pro-inflammatory factor interleukin-8 (IL-8) is related to poor prognosis in hepatocellular carcinoma (HCC) patients. Interleukin-8 enhanced HCC invasion by upregulating Snail and Twist1, whether this modulation relies on microRNAs (miR) is unclear. In this study, hsa-miR-370-3p was screened as candidate miRNA targeting Snail and Twist1, and its expression was downregulated by IL-8. Luciferase assays and RNA electrophoretic mobility shift assays were used to evaluate the interaction between miR-370-3p and targeted mRNAs. Coimmunoprecipitation, luciferase, and ChIP assays were undertaken to investigate the mechanisms underlying IL-8-mediated modification of miR-370-3p. Gain- and loss-of-function studies, Transwell assays, and a xenograft nude mouse model were used to investigate pro- and antitumor activities. Interleukin-8 and miR-370-3p levels were analyzed for clinical relevance in HCC patients. Our results showed that HCC patients with high levels of IL-8 experienced more metastasis and shorter survival. Interleukin-8 induced epithelial-mesenchymal transition and promoted liver cancer cell migration, invasion, and metastasis both in vitro and in vivo. MicroRNA-370-3p interacted with its cognate mRNA within the 3'-UTR regions of Twist1 and Snail mRNA directly and specifically and attenuated IL-8 protumoral effects on liver cancer cells. Interleukin-8 negatively modulated miR-370-3p through signal transducer and activator of transcription 3 (STAT3) activation by recruiting histone deacetylase 1 (HDAC1) to miR-370-3p promoter. The STAT3 and HDAC antagonists inhibited liver cancer cell migration and invasion. Patients with high miR-370-3p and low IL-8 levels had longer overall survival. In conclusion, our study elucidated a novel axis IL-8/STAT3/miR-370-3p/Twist1 and Snail relying on HDAC1 recruitment, which showed both diagnostic and therapeutic potentials of miR-370-3p in HCC metastasis.

Neuroendocrine microRNAs linked to energy homeostasis: future therapeutic potential

The brain orchestrates whole-body metabolism through an intricate system involving interneuronal crosstalk and communication. Specifically, a key player in this complex circuitry is the hypothalamus that controls feeding behaviour, energy expenditure, body weight and metabolism, whereby hypothalamic neurons sense and respond to circulating hormones, nutrients, and chemicals. Dysregulation of these neurons contributes to the development of metabolic disorders, such as obesity and type 2 diabetes. The involvement of hypothalamic microRNAs, post-transcriptional regulators of gene expression, in the central regulation of energy homeostasis has become increasingly apparent, although not completely delineated. This review summarizes current evidence demonstrating the regulation of feeding-related neuropeptides by brain-derived microRNAs as well as the regulation of specific miRNAs by nutrients and other peripheral signals. Moreover, the involvement of microRNAs in the central nervous system control of insulin, leptin, and estrogen signal transduction is examined. Finally, the therapeutic and diagnostic potential of microRNAs for metabolic disorders will be discussed and the regulation of brain-derived microRNAs by nutrients and other peripheral signals is considered. Demonstrating a critical role of microRNAs in hypothalamic regulation of energy homeostasis is an innovative route to uncover novel biomarkers and therapeutic candidates for metabolic disorders.

Tumor Suppressor microRNAs in Gastrointestinal Cancers: A Mini-Review

BACKGROUND

Gastrointestinal (GI) cancer is associated with a group of cancers affecting the organs in the GI tract, with a high incidence and mortality rate. This type of cancer development involves a series of molecular events that arise by the dysregulation of gene expressions and microRNAs (miRNAs).

OBJECTIVES

This mini-review focuses on elucidating the mechanism of tumor suppressor miRNA-mediated oncogenic gene silencing, which may contribute to a better understanding of miRNA-mediated gene expression regulation of cell cycle, proliferation, invasion, and apoptosis in GI cancers. In this review, the biological significance of tumor suppressor miRNAs involved in gastrointestinal cancers is briefly explained.

METHODS

The articles were searched with the keywords 'miRNA', 'gastrointestinal cancers', 'esophageal cancer', 'gastric cancer', 'colorectal cancer', 'pancreatic cancer', 'liver cancer', and 'gall bladder cancer' from the Google Scholar and PubMed databases. A total of 71 research and review articles have been collected and referred for this study.

RESULTS

This review summarises recent research enhancing the effectiveness of miRNAs as novel prognostic, diagnostic, and therapeutic markers for GI cancer treatment strategies. The expression pattern of various miRNAs has been dysregulated in GI cancers, which are associated with proliferation, cell cycle regulation, apoptosis, migration, and invasion.

CONCLUSION

The role of tumor suppressor miRNAs in the negative regulation of oncogenic gene expression was thoroughly explained in this review. Its potential role as a microRNA therapeutic candidate is also discussed. Profiling and regulating tumor suppressor miRNA expression in gastrointestinal cancers using miRNA mimics could be used as a prognostic, diagnostic, and therapeutic marker, as well as an elucidating molecular therapeutic approach to tumor suppression.

Epithelial-mesenchymal transition process during embryo implantation

The epithelial to mesenchymal transition (EMT) in endometrial epithelial and trophectoderm cells is essential for the progression of embryo implantation and its impairment could cause implantation failure. Therefore, EMT should be tightly regulated in both embryonic and endometrial cells during implantation. Studies reported the involvement of numerous factors in EMT regulation, including hormones, growth factors, transcription factors, microRNAs, aquaporins (AQPs), and ion channels. These factors act through different signaling pathways to affect the expression of epithelial and mesenchymal markers as well as the cellular cytoskeleton. Although the mechanisms involved in cancer cell EMT have been well studied, little is known about EMT during embryo implantation. Therefore, we comprehensively reviewed different factors that regulate the EMT, a key event required for the conceptus implantation to the endometrium.Summary sentence: Abnormal epithelial-mesenchymal transition (EMT) process within endometrial epithelial cells (EECs) or trophoblast cells can cause implantation failure. This process is regulated by various factors. Thus, the objective of this review was to summarize the effective factors on the EMT process during implantation.

CircRNAs: Insights into Gastric Cancer

Background

Gastric cancer (GC) is recorded as the fifth most common cancer globally. The classic resemblance of early symptoms of chronic gastritis including nausea, dysphagia, and dyspepsia with GC is the current challenge limiting the early diagnosis of GC. The current diagnostic procedures of GC are limited due to their invasive nature. This directs the research question toward alternative approaches, specifically at the molecular level. Recent advances in molecular regulation of cancer suggest the prominence of circular RNAs (circRNAs) in the multistep process of tumourigenesis.

Summary

CircRNAs are a class of non-coding RNAs, abundant in eukaryotes, with key roles in regulating genes and miRNAs as well as the alteration of processes involved in pathological conditions. Research studies have demonstrated the participation of circRNAs in the initiation and progression of tumours. This review provides a comprehensive insight into the potential of circRNAs as disease biomarkers for the early detection and treatment of GC.

Key Messages

This study is an amalgamation of the implications and future prospects of circRNAs for the detection and potential treatment of GC.

Recent research progress on circular RNAs: Biogenesis, properties, functions, and therapeutic potential

Circular RNAs (circRNAs), an emerging family member of RNAs, have gained importance in research due to their new functional roles in cellular physiology and disease progression. circRNAs are usually available in a wide range of cells and have shown tissue-specific expression as well as developmental specific expression. circRNAs are characterized by structural stability, conservation, and high abundance in the cell. In this review, we discuss the different models of biogenesis. The properties of circRNAs such as localization, structure and conserved pattern, stability, and expression specificity are also been illustrated. Furthermore, we discuss the biological functions of circRNAs such as microRNA (miRNA) sponging, cell cycle regulation, cell-to-cell communication, transcription regulation, translational regulation, disease diagnosis, and therapeutic potential. Finally, we discuss the recent research progress and future perspective of circRNAs. This review provides an understanding of potential diagnostic markers and the therapeutic potential of circRNAs, which are emerging daily.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

m6 A modification of lncRNA PCAT6 promotes bone metastasis in prostate cancer through IGF2BP2-mediated IGF1R mRNA stabilization

BACKGROUND

Bone metastasis is the leading cause of tumor-related death in prostate cancer (PCa) patients. Long noncoding RNAs (lncRNAs) have been well documented to be involved in the progression of multiple cancers. Nevertheless, the role of lncRNAs in PCa bone metastasis remains largely unclear.

METHODS

The expression of prostate cancer-associated transcripts was analyzed in published datasets and further verified in clinical samples and cell lines by RT-qPCR and in situ hybridization assays. Colony formation assay, MTT assay, cell cycle analysis, EdU assay, Transwell migration and invasion assays, wound healing assay, and in vivo experiments were carried out to investigate the function of prostate cancer-associated transcript 6 (PCAT6) in bone metastasis and tumor growth of PCa. Bioinformatic analysis, RNA pull-down, and RIP assays were conducted to identify the proteins binding to PCAT6 and the potential targets of PCAT6. The therapeutic potential of targeting PCAT6 by antisense oligonucleotides (ASO) was further explored in vivo.

RESULTS

PCAT6 was upregulated in PCa tissues with bone metastasis and increased PCAT6 expression predicted poor prognosis in PCa patients. Functional experiments found that PCAT6 knockdown significantly inhibited PCa cell invasion, migration, and proliferation in vitro, as well as bone metastasis and tumor growth in vivo. Mechanistically, METTL3-mediated m6 A modification contributed to PCAT6 upregulation in an IGF2BP2-dependent manner. Furthermore, PCAT6 upregulated IGF1R expression by enhancing IGF1R mRNA stability through the PCAT6/IGF2BP2/IGF1R RNA-protein three-dimensional complex. Importantly, PCAT6 inhibition by ASO in vivo showed therapeutic potential against bone metastasis in PCa. Finally, the clinical correlation of METTL3, IGF2BP2, IGF1R, and PCAT6 was further demonstrated in PCa tissues and cells.

CONCLUSIONS

Our study uncovers a novel molecular mechanism by which the m6 A-induced PCAT6/IGF2BP2/IGF1R axis promotes PCa bone metastasis and tumor growth, suggesting that PCAT6 may serve as a promising prognostic marker and therapeutic target against bone-metastatic PCa.

emiRIT: a text-mining-based resource for microRNA information

microRNAs (miRNAs) are essential gene regulators, and their dysregulation often leads to diseases. Easy access to miRNA information is crucial for interpreting generated experimental data, connecting facts across publications and developing new hypotheses built on previous knowledge. Here, we present extracting miRNA Information from Text (emiRIT), a text-miningbased resource, which presents miRNA information mined from the literature through a user-friendly interface. We collected 149 ,233 miRNA –PubMed ID pairs from Medline between January 1997 and May 2020. emiRIT currently contains ‘miRNA –gene regulation’ (69 ,152 relations), ‘miRNA disease (cancer)’ (12 ,300 relations), ‘miRNA –biological process and pathways’ (23, 390 relations) and circulatory ‘miRNAs in extracellular locations’ (3782 relations). Biological entities and their relation to miRNAs were extracted from Medline abstracts using publicly available and in-house developed text-mining tools, and the entities were normalized to facilitate querying and integration. We built a database and an interface to store and access the integrated data, respectively. We provide an up-to-date and user-friendly resource to facilitate access to comprehensive miRNA information from the literature on a large scale, enabling users to navigate through different roles of miRNA and examine them in a context specific to their information needs. To assess our resource’s information coverage, we have conducted two case studies focusing on the target and differential expression information of miRNAs in the context of cancer and a third case study to assess the usage of emiRIT in the curation of miRNA information.

Database URL: https://research.bioinformatics.udel.edu/emirit/

MicroRNA-135b/CAMK2D Axis Contribute to Malignant Progression of Gastric Cancer through EMT Process Remodeling

There is a continued need for investigating the roles of microRNAs (miRNAs) and their targets on the progression of gastric cancer (GC), especially metastasis. Here, we performed an integrated study to identify dysregulated miRNAs critical for GC development and progression. miR-135b was determined as a promising biomarker for GC. The expression level of miR-135b was increased among GC cell lines, patient tumor tissues, serum samples, and correlation with aggravation of the GC patients. The in vitro functional assays demonstrated overexpression of miR-135b promoted cell proliferation, migration and invasion in GC, while miR-135b inhibition led to the opposite results. CAMK2D was found to be the direct target of miR-135b, serving as a tumor suppressor in GC cells. Based on our and public datasets, we confirmed the attenuation of CAMK2D expression in GC tissues. And, the expression levels of miR-135b and CAMK2D were closely associated with prognosis of GC patients. Ectopic expression of miR-135b resulted in the down-regulation of CAMK2D. Additionally, CAMK2D was a prerequisite for miR-135b to promote GC cells proliferation and migration by regulating the EMT process, which was confirmed by the in vivo experiments. Importantly, in vivo injection of miR-135b antagomir significantly repressed the tumor growth and metastasis of xenograft models, which suggested that the miR-135b antagomir were promising for clinical applications. Taken together, these results indicate that miR-135b/CAMK2D axis drives GC progression by EMT process remodeling, suggesting that miR-135b may be utilized as a new therapeutic target and prognostic marker for GC patients.

A four-lncRNA signature for predicting prognosis of recurrence patients with gastric cancer

Purpose

This study aimed to develop a multi-long noncoding RNA (lncRNA) signature for the prediction of gastric cancer (GC) based on differential gene expression between recurrence and nonrecurrence patients.

Methods

By repurposing microarray expression profiles of RNAs from The Cancer Genome Atlas (TCGA), we performed differential expression analysis between recurrence and nonrecurrence patients. A prognostic risk prediction model was constructed based on data from TCGA database, and its reliability was validated using data from Gene Expression Omnibus database. Furthermore, the lncRNA-associated competing endogenous RNA (ceRNA) network was constructed, namely, DIANA-LncBasev2 and starBase database.

Results

We identified 363 differentially expressed RNAs (317 mRNAs, 18 lncRNAs, and 28 microRNAs [miRNAs]). Principal component analysis showed that the seven-feature lncRNAs screened by support vector machine-recursive feature elimination algorithm was more informative for predicting recurrence of GC in comparison with the eight-feature lncRNAs screened by random forest-out-of-bag algorithm. Four of the seven-feature lncRNAs including LINC00843, SNHG3, C21orf62-AS1, and MIR99AHG were chosen to develop a four-lncRNA risk score model. This risk score model was able to distinguish patients with high and low risk of recurrence, and was tested in two independent validation sets. The ceRNA network of this four-lncRNA signature included 10 miRNAs and 178 mRNAs. The mRNAs significantly related to the Wnt-signaling pathway and relevant biological processes.

Conclusion

A useful four-lncRNA signature recurrence was established to distinguish GC patients with high and low risk of recurrence. Regulating the relevant miRNAs and Wnt pathway might partly affect GC metastasisby.

The Multifaceted Role and Utility of MicroRNAs in Indolent B-Cell Non-Hodgkin Lymphomas

Normal B-cell development is a tightly regulated complex procedure, the deregulation of which can lead to lymphomagenesis. One common group of blood cancers is the B-cell non-Hodgkin lymphomas (NHLs), which can be categorized according to the proliferation and spread rate of cancer cells into indolent and aggressive ones. The most frequent indolent B-cell NHLs are follicular lymphoma and marginal zone lymphoma. MicroRNAs (miRNAs) are small non-coding RNAs that can greatly influence protein expression. Based on the multiple interactions among miRNAs and their targets, complex networks of gene expression regulation emerge, which normally are essential for proper B-cell development. Multiple miRNAs have been associated with B-cell lymphomas, as the deregulation of these complex networks can lead to such pathological states. The aim of the present review is to summarize the existing information regarding the multifaceted role of miRNAs in indolent B-cell NHLs, affecting the main B-cell subpopulations. We attempt to provide insight into their biological function, the complex miRNA-mRNA interactions, and their biomarker utility in these malignancies. Lastly, we address the limitations that hinder the investigation of the role of miRNAs in these lymphomas and discuss ways that these problems could be overcome in the future.

MiR-7 in Cancer Development

MicroRNAs (miRNAs) are short non-coding RNA involved in the regulation of specific mRNA translation. They participate in cellular signaling circuits and can act as oncogenes in tumor development, so-called oncomirs, as well as tumor suppressors. miR-7 is an ancient miRNA involved in the fine-tuning of several signaling pathways, acting mainly as tumor suppressor. Through downregulation of PI3K and MAPK pathways, its dominant role is the suppression of proliferation and survival, stimulation of apoptosis and inhibition of migration. Besides these functions, it has numerous additional roles in the differentiation process of different cell types, protection from stress and chromatin remodulation. One of the most investigated tissues is the brain, where its downregulation is linked with glioblastoma cell proliferation. Its deregulation is found also in other tumor types, such as in liver, lung and pancreas. In some types of lung and oral carcinoma, it can act as oncomir. miR-7 roles in cell fate determination and maintenance of cell homeostasis are still to be discovered, as well as the possibilities of its use as a specific biotherapeutic.

circHIPK3 regulates proliferation and differentiation of myoblast through the miR-7/TCF12 pathway

Skeletal muscle development is a complex biological process involving multiple key genes, signaling pathways and noncoding RNAs, including microRNAs and circular RNAs (circRNAs). However, the regulatory relationship among them is so complicated that it has not yet been fully elucidated. In this study, we found that miR-7 inhibited C2C12 cell proliferation and differentiation by targeting transcription factor 12 (TCF12). circHIPK3 acted as a competing endogenous RNA, and its overexpression effectively reversed the regulation of miR-7 on C2C12 cell proliferation and differentiation by increasing TCF12 expression. Taken together, our findings provide evidence that circHIPK3 regulates skeletal muscle development through the miR-7/TCF12 pathway. This study provides a scientific basis for further research on skeletal muscle development at the circRNA level.

Metformin mediated microRNA-7 upregulation inhibits growth, migration, and invasion of non-small cell lung cancer A549 cells

Metformin, a medication widely used in the treatment of type 2 diabetes mellitus, has a possible antitumor effect in type 2 diabetes mellitus patients. MicroRNA-7 is a significant microRNA in non-small cell lung cancer. Metformin has an inhibitory effect on lung cancer and regulates the expression of certain microRNAs, but there is no report connecting metformin with microRNA-7 in lung cancer. Thus, we used qPCR to measure microRNA-7 expression in A549 non-small cell lung cancer cells treated with metformin. We used CCK8, cell scratch, and Transwell assays to test the growth, migration, and invasion of A549 cells. Western blotting was used to measure the expression level of relevant proteins in A549 cells. We found that microRNA-7 was dramatically upregulated by metformin via AMPK in a dose- and time-dependent manner. Both metformin and microRNA-7 mimic reduced A549 cell growth, migration, and invasion. Metformin downregulated the levels of p-NF-κB p65, p-Erk1/2, p-AKT, and p-mTOR proteins. The treatment with the microRNA-7 mimic had the same result. The decrease of these proteins caused the inhibition of A549 cell growth, migration, and invasion. Our discovery revealed that metformin, via increasing the expression of microRNA-7 mediated by AMPK, regulates the AKT/mTOR, MAPK/Erk, and NF-κB signaling pathways, thereby suppressing A549 cell growth, migration, and invasion.

Underlying metastasis mechanism and clinical application of exosomal circular RNA in tumors (Review)

Circular RNA (circRNA) is a long non-coding RNA molecule with a closed loop structure lacking a 5′cap and 3′tail. circRNA is stable, difficult to cleave and resistant to RNA exonuclease or RNase R degradation. circRNA molecules have several clinical applications, especially in tumors. For instance, circRNA may be used for non-invasive diagnosis, therapy and prognosis. Exosomes play a crucial role in the development of tumors. Exosomal circRNA in particular has led to increased research interest into tumorigenesis and tumor progression. Additionally, exosomal circRNA plays a role in cell-cell communication. Exosomal circRNA facilitates tumor metastasis by altering the tumor microenvironment and the pre-metastatic niche. Additionally, studies have revealed the mechanism by which exosomal circRNA affects malignant progression through signal transduction. Moreover, exosomal circRNA promotes tumor metastasis by regulating gene expression, RNA transcription and protein translation. In this review, the biological features and clinical application of exosomal circRNA are described, highlighting the underlying mechanisms through which they regulate tumor metastasis. The application of circRNA as clinical diagnostic biomarkers and in the development of novel therapeutic strategies is also discussed.

MicroRNA-367-3p induces apoptosis and suppresses migration of MCF-7 cells by downregulating the expression of human choline kinase α

Choline kinase (ChK) catalyzes the first step in the CDP-choline pathway for the synthesis of phosphatidylcholine. The α isoform of this enzyme is overexpressed in various types of cancer and its inhibition or downregulation has been applied as an anticancer strategy. In spite of increasing attention being paid to ChK expression, as well as its activity and inhibition in cancer, there are only limited studies available on the regulation of ChK, including its regulation by microRNAs (miRNAs/miRs). The dysregulation of gene expression by miRNAs is a common cause for carcinogenesis. In the present study, miR-367-3p was predicted to target the 3′-untranslated region (UTR) of the ChK α (chka) mRNA transcript. The binding of miR-367-3p to the 3′-UTR of chka was validated by a luciferase assay. The effects of the miR-367-3p mimic on chka gene and protein expression levels were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. miR-367-3p significantly downregulated the expression of chka to ~60% of the negative control. Cells transfected with miR-367-3p exhibited higher levels of apoptosis and a lower cell migration compared with the control. To the best of our knowledge, the present study provided the first experimental evidence of the regulation of chka expression by miR-367-3p. The pro-apoptotic and suppressive effects of miR-367-3p on cell migration were similar to the anticancer effects resulting from the inhibition of ChK enzyme activity or the knockdown of chka gene expression by small interfering RNA. Therefore, these findings may potentially lead to the use of miR-367-3p in anticancer strategies that target ChK.

miR‑7/SP1/TP53BP1 axis may play a pivotal role in NSCLC radiosensitivity

MicroRNA‑7 (miR‑7) has been identified as a tumor suppressor in non‑small cell lung cancer (NSCLC) and a radiosensitivity regulator. Numerous studies have revealed that specific protein 1 (SP1) plays a critical role in the tumorigenesis of various types of cancers and regulates radiosensitivity and tumor suppressor p53‑binding protein 1 (TP53BP1), which plays an essential role in DNA repair. However, it is not clear whether miR‑7 has a regulatory effect on SP1 and TP53BP1 in NSCLC. In the present study it was revealed that miR‑7 directly binds to the 3'UTR of SP1, thereby suppressing SP1 expression to regulate radiosensitivity. Overexpression of miR‑7 and SP1 and knockdown of miR‑7 and SP1 were performed using lentiviral transfection. Protein and mRNA abundance of SP1 and TP53BP1 were determined using western blotting and RT‑qPCR, respectively, while miR‑7 binding to SP1 was validated using a luciferase reporter assay. Biological function analysis indicated that miR‑7 negatively regulated SP1 and inhibited cell proliferation, migration, and invasion when combined with radiation. It was also revealed that the expression of TP53BP1 was positively regulated by SP1 or negatively regulated by miR‑7. In conclusion, SP1 was a target of miR‑7, and the decreased expression of SP1 resulting from miR‑7 overexpression in NSCLC was vital for improving radiosensitivity in NSCLC cells. Moreover, SP1 expression was detected in 95 paired NSCLC and adjacent normal tissues, and it was determined that SP1 was significantly upregulated in NSCLC tissues and that its upregulation was correlated with the degree of tissue differentiation. Thus, SP1 and/or miR‑7 may be potential molecular targets in NSCLC radiotherapy.

Circular RNA Circ-03955 Promotes Epithelial-Mesenchymal Transition in Osteosarcoma by Regulating miR-3662/Metadherin Pathway

Osteosarcoma is the most common primary malignant tumor, especially in children and adolescents. Circular RNAs (circRNAs) are found to play roles in the progression of osteosarcoma. However, the exact functions of circRNAs in osteosarcoma development still need to be clarified. We obtained differentially expressed circRNAs and miRNAs from a GSE99671 data set (GEO database). The gene co-expression network of ceRNAs and osteosarcoma-related genes was analyzed using the STRING database. qRT-PCR was used to detect the expression of circ-03955 and miR-3662. Transwell assays and flow cytometry were performed to detect phenotypic changes in cell function. A xenograft tumor model was established using BALB/c nude mice. Dual luciferase activity and RNA immunoprecipitation assays were performed to assess the relationship between circ-03955, miR-3662, and metadherin (MTDH). Immunohistochemistry, immunofluorescence, and Western blotting were used to assess protein expression levels. Circ-03955 was significantly upregulated, and miR-3662 was downregulated in osteosarcoma. Circ-03955 silencing inhibited the growth and metastasis of osteosarcoma. Mechanism analysis revealed that circ-03955 could bind to miR-3662, and the latter could target MTDH, leading to its suppressed expression and facilitating epithelial-mesenchymal transition (EMT). All these findings demonstrate that the presence of circ-03955 promotes EMT in osteosarcoma by acting as miR-3662 sponge-mediated MTDH expression.

MicroRNA in Gastric Cancer Development: Mechanisms and Biomarkers

Gastric cancer (GC) is one of the most common and difficult diseases to treat. The study of signaling pathway regulation by microRNA provides information on the mechanisms of GC development and is the basis for biomarker creation. In this study, a circuit of microRNA interactions with signaling pathways was constructed. The microRNAs, associated with metastasis and chemoresistance, are described. In most cases, microRNAs in GC regulate the Wnt/β-catenin, PI3K/AKT/mTOR, RAS/RAF/ERK/MAPK, NF-kB, TGF-β, and JAK/STAT pathways. Part of the microRNA acts on several target genes that function in different pathways. This often leads to an intensification of the induced processes. MicroRNAs have also been described that have the opposite effect on different pathways, causing different functional consequences. By acting on several target genes, or genes associated with several pathways, microRNAs can function in a signaling network. MicroRNAs associated with metastasis most often interact with the Wnt/β-catenin pathway. MicroRNAs affecting chemoresistance, in most cases, affect the regulators of apoptosis and are associated with the PI3K/AKT/mTOR pathway. The characteristics of microRNAs proposed as candidates for GC biomarkers were analyzed. The currently developed diagnostic and prognostic panels of microRNAs are also considered.

Molecular mechanisms underlining the role of metformin as a therapeutic agent in lung cancer

BACKGROUND

Metformin, a first-line therapeutic for type 2 diabetes, has been studied for its potential use in cancer treatment following a number of epidemiological studies that have demonstrated reduced cancer incidence and mortality rates among patients treated with the drug. As yet, however, there remains significant uncertainty about the molecular mechanisms by which metformin exerts its anti-cancer effects. Herein, we summarize the evidence surrounding the anti-lung cancer effects of metformin.

CONCLUSIONS

Specifically, we explore protein targets of metformin, including AMPK, PP2A, IRF-1/YAP and HGF and we outline the proposed mechanisms of action for metformin in lung cancer, with particular attention given to apoptosis and autophagy. We also closely examine the synergistic activity of metformin with existing cancer treatment regimens, such as TKI's, platinum-based agents and immune therapeutics. In addition to considering preclinical and clinical studies, we also dissect and contextualize the limitations and inconsistencies of the current literature, especially those of epidemiological studies. Finally, we offer a potential trajectory for future research in this rapidly evolving area of basic and clinical oncology.

Elevated microRNA-7 inhibits proliferation and tumor angiogenesis and promotes apoptosis of gastric cancer cells via repression of Raf-1

OBJECTIVE

Since the essential involvement of microRNAs (miRNAs) in the development and progression of GC, the study was for the exploration of the value of microRNA-7 (miR-7) in the evaluation of neoadjuvant chemotherapy for gastric cancer (GC) and its effects on apoptosis, proliferation and angiogenesis of GC.

METHODS

miR-7 expression in serum of GC patients before and after neoadjuvant chemotherapy were detected to explore its role in neoadjuvant chemotherapy of GC. The GC cells were transfected with miR-7 mimics/inhibitors, or siRNA-Raf-1 to figure out their roles in proliferation, migration, invasion, cycle distribution and apoptosis. Tumor xenograft was conducted to test tumor growth. Microvessel density (MVD) in tumors was tested by immunohistochemical staining.

RESULTS

miR-7 expression in serum of GC patients was lower than that of healthy controls while it was elevated after neoadjuvant chemotherapy. Moreover, higher miR-7 expression was exhibited in chemotherapy-effective patients rather than chemotherapy-ineffective patients (P < 0.01). miR-7 expression in serum was connected with tumor size, degree of differentiation, TNM stage and lymphatic metastasis.miR-7 was decreased and Raf-1 was elevated in GC cells (both P < 0.05). Elevated miR-7 or declined Raf-1 inhibited GC cell migration, proliferation and invasion, cell cycle entry, xenografted tumor growth and MVD and stimulated apoptosis (all P < 0.05). Down-regulated Raf-1 reversed the impacts of miR-7 knockdown on GC cells (all P < 0.05).

CONCLUSION

Our study highlights that elevated miR-27a indicates the good efficacy of neoadjuvant chemotherapy in GC and miR-7 targets Raf-1 to suppress tumor development and angiogenesis of GC cells.

Down-Regulation of miR-7 in Gastric Cancer Is Associated With Elevated LDH-A Expression and Chemoresistance to Cisplatin

MicroRNAs (miRNAs) are dysregulated in the context of many cancer types, making them potentially ideal diagnostic or therapeutic targets in patients in which they are aberrantly expressed. In the present study, we found miR-7 to be downregulated in gastric cancer (GC), and we further determined its expression to be closely linked to GC sensitivity to the chemotherapeutic compound cisplatin. This effect appears to be at least partially attributable to the regulation of LDH-A, which is a miR-7 target gene and expression of LDH-A is negatively correlated with miR-7 expression in primary GC tumor samples. When upregulated, we also determined that miR-7 was able to inhibit the proliferation, colony formation, and glycolysis of GC cells owing to its regulation of LDH-A. Moreover, overexpression of miR-7 render cells more sensitive to cisplatin. Our results thus provide novel evidence that miR-7 is a key mediator of GC growth and chemosensitivity through its regulation of LDH-A, thus potentially highlighting this pathway as a therapeutic target for treating affected patients.

CiRS-7 functions as a ceRNA of RAF-1/PIK3CD to promote metastatic progression of oral squamous cell carcinoma via MAPK/AKT signaling pathways

PURPOSE

Recent findings have shown that circRNA dysregulation was involved in the development of many types of cancer. However, our knowledge of circRNA in oral squamous cell carcinoma (OSCC) remains elusive.

METHODS

Here, we explored whether ciRS-7 could function as a ceRNA in promoting metastasis of OSCC via regulating miR-7 activity. The expression levels of ciRS-7 and miR-7 were examined in clinical samples and cell lines by qRT-PCR, and the effects of ectopic expression of ciRS-7 and miR-7 on cell proliferation, migration and invasion were assessed in vitro and in vivo. The effects of ciRS-7 on miR-7 activity were investigated by means of luciferase reporter assay, qRT-PCR and Western blot. In addition, the effects of miR-7 mediated ciRS-7 on the levels of MAPK/AKT signaling proteins were evaluated by Western blot.

RESULTS

We found that ciRS-7 was highly expressed in OSCC tissues and cell lines compared with normal counterparts. Ectopic expression of ciRS-7 significantly promoted OSCC cell proliferation, migration and invasion through in vitro and in vivo. Based on bioinformatics analysis, qRT-PCR, Western blot and luciferase reporter assays, we determined that ciRS-7 functioned as a sponge for miR-7, resulting in attenuation of miR-7 targets RAF-1 and PIK3CD, which are core components of the MAPK/AKT signaling pathways. Moreover, miR-7 correlated with perineural and lymphovascular invasion in OSCC patients. Further experiments demonstrated that ciRS-7 overexpression could attenuate the anti-tumor effects of miR-7 on OSCC cells.

CONCLUSIONS

Our results suggested that ciRS-7 can interact directly with miR-7, resulting in upregulation of RAF-1/PIK3CD expression and enhancing metastatic progression of OSCC.

Spatial expression analyses of the putative oncogene ciRS-7 in cancer reshape the microRNA sponge theory

Circular RNAs (circRNAs) have recently gained substantial attention in the cancer research field where most, including the putative oncogene ciRS-7 (CDR1as), have been proposed to function as competitive endogenous RNAs (ceRNAs) by sponging specific microRNAs. Here, we report the first spatially resolved cellular expression patterns of ciRS-7 in colon cancer and show that ciRS-7 is completely absent in the cancer cells, but highly expressed in stromal cells within the tumor microenvironment. Additionally, our data suggest that this generally apply to classical oncogene-driven adenocarcinomas, but not to other cancers, including malignant melanoma. Moreover, we find that correlations between circRNA and mRNA expression, which are commonly interpreted as evidence of a ceRNA function, can be explained by different cancer-to-stromal cell ratios among the studied tumor specimens. Together, these results have wide implications for future circRNA studies and highlight the importance of spatially resolving expression patterns of circRNAs proposed to function as ceRNAs.

Role of microRNA-7 in liver diseases: a comprehensive review of the mechanisms and therapeutic applications

MicroRNA-7 (miR-7) is a small non-coding RNA, which plays critical roles in regulating gene expression of multiple key cellular processes. MiR-7 exhibits a tissue-specific pattern of expression, with abundant levels found in the brain, spleen, and pancreas. Although it is expressed at lower levels in other tissues, including the liver, miR-7 is involved in both the development of organs and biological functions of cells. In this review, we focus on the mechanisms by which miR-7 controls cell growth, proliferation, invasion, metastasis, metabolism, and inflammation. We also summarize the specific roles of miR-7 in liver diseases. MiR-7 is considered as a tumor suppressor miRNA in hepatocellular carcinoma and is involved in the pathogenesis of hepatic steatosis and hepatitis. Future studies to further define miR-7 functions and its mechanism in association with other types of liver diseases should be explored. An improved understanding from these studies will provide us a useful perspective leading to mechanism-based intervention by targeting miR-7 for the treatment of liver diseases.

MicroRNA-7 as a Potential Biomarker for Prognosis in Pancreatic Cancer

MicroRNAs play critical roles in tumor progression. Our recent study has indicated that microRNA-7 (miR-7) impairs autophagy-derived pools of glucose to suppress the glycolysis in pancreatic cancer progression. However, the roles of miR-7 in clinical significance and chemoresistance of pancreatic cancer remain unexplored. The aim of this study was to assess the expression of miR-7 in patients with pancreatic cancer and to evaluate the possibility of its usage as a prognostic molecular biomarker. MicroRNA array-based quantification analysis of 372 miRNAs was compared in serum between pancreatic cancer and healthy individuals, gemcitabine-sensitive and gemcitabine-resistance patients. We identified miR-7 showed the potential predictive power for gemcitabine-sensitive patients with pancreatic cancer. Then, the results were validated in pancreatic tissue microarray and The Cancer Genome Atlas (TCGA) dataset, demonstrating that lower miR-7 expression was correlated with more advanced tumor stages and worse prognosis in pancreatic cancer. The Cox proportional-hazards model analysis identified miR-7 to be an independent variable for prediction of the survival. Furthermore, the mechanistic exploration suggested the clinical significance of miR-7 involved its interference effect on autophagy and glycolysis in pancreatic cancer using pancreatic cancer tissue microarrays and TCGA data. Therefore, the results of the present study provide evidences that low microRNA-7 expression may contribute to tumor progression and poor prognosis in pancreatic cancer.

MiR-200b Inhibits Tumor Growth and Chemoresistance via Targeting p70S6K1 in Lung Cancer

Downregulation of microRNA-200b (miR-200b) has been identified in a range of cancers, yet the specific mechanisms whereby it influences lung cancer growth require further exploration. We determined that lung cancer patient tumor samples exhibit decreased miR-200b expression, and we further found this miRNA to inhibit tumor growth via interfering with ERK1/2 and AKT signaling, targeting p70S6K1 to suppress HIF-1α expression. This miRNA further rendered H1299 cells more sensitive to cisplatin while impairing their proliferative and invasive potential through its ability to target and inhibit the activity of p70S6K1. These results were further confirmed in a murine xenograft model in which miR-200b also inhibited the growth of tumor and suppressed p70S6K1, p-AKT, p-ERK1/2, and HIF-1α expression. These findings clearly demonstrate a role for miR-200b in suppressing lung cancer development, making it a potentially relevant target for future diagnostic and therapeutic interventions.

The N-terminal polypeptide derived from vMIP-II exerts its antitumor activity in human breast cancer through CXCR4/miR-7-5p/Skp2 pathway

Breast cancer is a malignant tumor with the highest incidence in women of the world. CXCR4 and Skp2 are highly expressed in breast cancer cells and CXCR4 was positively correlated with Skp2 by interference or overexpression. The microRNA array was used to detect the differentially expressed spectrum of micro RNAs in breast cancer cells the changes of miR-7-5p after CXCR4 inhibitor (NT21MP) treatment to block the CXCR4/SDF-1 pathway was founded. MiR-7-5p has been found to be correlated with Skp2 in various tumors in the literature, and Skp2 expression can be regulated by transfection with miR-7-5p mimics or inhibitors. The expression level of miR-7-5p was upregulated or downregulated after CXCR4 interference or overexpression. Combined with the correlation between CXCR4 and miR-7-5p in the chip results, CXCR4 may regulate Skp2 through miR-7-5p. Epithelial cells have the morphological characteristics of mesenchymal cells for some reason called epithelial-mesenchymal transformation (EMT). Transfection of miR-7-5p mimics into drug-resistant cells reduced Skp2 levels, decreased the expression of Vimentin, Snail, and slug, and increased the expression of E-cadherin. CXCR4 inhibitor (NT21MP) can reverse the EMT changes caused by miR-7-5p inhibitor. Similarly, in vivo results suggesting that CXCR4 inhibitors can reverse the EMT phenotype of drug-resistant breast cancer cells through the CXCR4/miR-7-5p/Skp2 pathway. In summary, the CXCR4/miR-7-5p/Skp2 signaling pathway plays an important role in the progression of breast cancer. This study provides a theoretical basis for the treatment of breast cancer by targeting the CXCR4 pathway.

Regulation of E2F Transcription Factor 3 by microRNA-152 Modulates Gastric Cancer Invasion and Metastasis

Background

The transcription factor, E2F transcription factor 3 (E2F3), has been proved to modulate metastasis in multiple human cancers. The present study was aimed to expound the function and specific mechanism of E2F3 in gastric cancer (GC) progression.

Materials and Methods

The expression of E2F3, microRNA-152 (miR-152) and PLK1 (polo-like kinase 1) in GC cell lines was detected by quantitative RT-PCR and Western blot. The roles of E2F3 and miR-152 in GC metastasis were classified using gain-of-function and loss-of-function assays. The miRNAs directly targeting E2F3 were identified by bioinformatics analysis and luciferase reporter experiment. Chromatin immunoprecipitation was carried out to reveal the correlation between E2F3 and PLK1.

Results

E2F3 expression was frequently up-regulated in GC tissues, and its high expression might imply poor prognosis. Downregulation of E2F3 restrained GC migration and invasion in vitro and in vivo. Interestingly, we proved that miR-152 was an upstream regulator of E2F3. Moreover, miR-152 reduced E2F3 expression by directly targeting its 3ʹ-UTR, and then modulated GC metastasis via polo-like kinase 1 (PLK1) mediated protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) signals.

Conclusion

E2F3 plays a crucial role in GC progression and the newly discovered miR-152/E2F3/PLK1 axis provides a new underlying target for therapy of metastasis in GC patients.

MiR-645 promotes invasiveness, metastasis and tumor growth in colorectal cancer by targeting EFNA5

MicroRNA-645 (miR-645) has been implicated in numerous types of human cancers including colon cancer. However, the effects and mechanisms of action of miR-645 dysregulation on the growth and malignancy of colorectal cancer (CRC) remain unclear. In this study, we demonstrated that miR-645 knockdown significantly diminished CRC cell migration and invasion and repressed epithelial-mesenchymal transition (EMT). Conversely, miR-645 overexpression enhanced CRC cell migration, invasion, and EMT. In vivo assays confirmed that miR-645 knockdown substantially reduced CRC growth and metastasis. Regarding the mechanism, ephrin-A5 (EFNA5) was identified as a direct target gene of miR-645. MiR-645 specifically targeted the 3'-untranslated region of EFNA5 mRNA and hindered its expression. EFNA5 knockdown attenuated the effects of miR-645 knockdown on CRC cell migration and invasion. Additionally, we noted a statistically significant inverse correlation between EFNA5 mRNA and miR-645 levels in tumors from 28 patients with CRC. Hence, miR-645 acts as an oncogenic miRNA that may increase CRC cell migration, invasiveness, and metastasis by targeting EFNA5.

MiR-501-3p functions as a tumor suppressor in non-small cell lung cancer by downregulating RAP1A

MicroRNA-501-3p (miR-501-3p) has been reported to play tumor-suppressive roles in different cancers; however, its expression pattern and biological function in non-small cell lung cancer (NSCLC) remain unknown. In this study, we noted downregulation of miR-501-3p in NSCLC tissues and cell lines. Functional assays showed that overexpression of miR-501-3p suppressed NSCLC cell proliferation, clonogenicity, migration, and invasion. Moreover, miR-501-3p overexpression attenuated in vivo tumor growth in a nude mouse model. In terms of the mechanism, RAP1A was identified as a novel target of miR-501-3p. Overexpression of RAP1A strongly attenuated the inhibitory effects of miR-501-3p on the capacity of NSCLC cells for proliferation and motility. In the clinical samples of NSCLC, miR-501-3p levels negatively correlated with RAP1A expression, which was upregulated in NSCLC. Collectively, these results indicate that miR-501-3p acts as a tumor suppressor in NSCLC by directly targeting RAP1A mRNA and may serve as a theranostic biomarker for patients with NSCLC.

The CDR1as/miR-7/TGFBR2 Axis Modulates EMT in Silica-Induced Pulmonary Fibrosis

Silicosis is one of the typical forms of pneumoconiosis characterized by abnormal proliferation of fibroblasts and deposition of extracellular matrix. Recent findings have shown that microRNAs and circular RNAs (circRNAs) are implicated in many diseases. However, the function of noncoding RNAs in pulmonary fibrosis remain to be elucidated. Here, miR-7 was found significantly decreased in silica-treated pulmonary epithelial cells as well as in fibrotic lung tissues of mice. Elevated expression of miR-7 via agomir injection relieved lung fibrosis in vivo. Further molecular study showed that miR-7 played its role against pulmonary fibrosis by blocking epithelial-mesenchymal transition (EMT) progression of human bronchial epithelial cells and A549 cells. Notably, transforming growth factor beta receptor 2 (TGFBR2) was identified as a target gene of miR-7 with bioinformatics tools, which was verified by dual luciferase receptor gene assay in human bronchial epithelial cells and A549 cells. Silica induced elevation of TGFBR2 could be abolished by exogenous expression of miR-7. Furthermore, bioinformatics software indicated that circRNA CDR1as had several binding sites for miR-7. The inhibitory effects of miR-7 on EMT and its target TGFBR2 were suppressed by circRNA CDR1as, which contributed to pulmonary fibrosis. Our studies also revealed overexpressed miR-7 could repress fibrogenesis of lung fibroblasts induced by TGF-β1. Collectively, circRNA CDR1as stimulated by silica could sponge miR-7 to release TGFBR2, plays an important role during pulmonary fibrosis by promoting EMT process. These results indicated that the interaction between miR-7 and circRNA CDR1as may exert important functions and provide potential therapeutic targets in lung fibrotic diseases.

miR-302a Inhibits Metastasis and Cetuximab Resistance in Colorectal Cancer by Targeting NFIB and CD44

Introduction: Metastasis and drug resistance contribute substantially to the poor prognosis of colorectal cancer (CRC) patients. However, the epigenetic regulatory mechanisms by which CRC develops metastatic and drug-resistant characteristics remain unclear. This study aimed to investigate the role of miR-302a in the metastasis and molecular-targeted drug resistance of CRC and elucidate the underlying molecular mechanisms.

Methods: miR-302a expression in CRC cell lines and patient tissue microarrays was analyzed by qPCR and fluorescence in situ hybridization. The roles of miR-302a in metastasis and cetuximab (CTX) resistance were evaluated both in vitro and in vivo. Bioinformatic prediction algorithms and luciferase reporter assays were performed to identify the miR-302a binding regions in the NFIB and CD44 3'-UTRs. A chromatin immunoprecipitation assay was performed to examine NFIB occupancy in the ITGA6 promoter region. Immunoblotting was performed to identify the EGFR-mediated pathways altered by miR-302a.

Results: miR-302a expression was frequently reduced in CRC cells and tissues, especially in CTX-resistant cells and patient-derived xenografts. The decreased miR-302a levels correlated with poor overall CRC patient survival. miR-302a overexpression inhibited metastasis and restored CTX responsiveness in CRC cells, whereas miR-302a silencing exerted the opposite effects. NFIB and CD44 were identified as novel targets of miR-302a. miR-302a inhibited the metastasis-promoting effect of NFIB that physiologically activates ITGA6 transcription. miR-302a restored CTX responsiveness by suppressing CD44-induced cancer stem cell-like properties and EGFR-mediated MAPK and AKT signaling. These results are consistent with clinical observations indicating that miR-302a expression is inversely correlated with the expression of its targets in CRC specimens.

Conclusions: Our findings show that miR-302a acts as a multifaceted regulator of CRC metastasis and CTX resistance by targeting NFIB and CD44, respectively. Our study implicates miR-302a as a candidate prognostic predictor and a therapeutic agent in CRC.

MicroRNA-4472 Promotes Tumor Proliferation and Aggressiveness in Breast Cancer by Targeting RGMA and Inducing EMT

BACKGROUND

Breast cancer is the most common cause of cancer-related death in women worldwide. MicroRNA (miRNA) ectopic expression has been reported to be involved in the regulation of gene expression in breast cancer. We screened several differentially expressed miRNAs associated with breast cancer chemoresistance, growth, and metastasis using a miRNA microarray. Increased expression of miR-4472 has been associated with larger breast tumors and chemoresistance. However, the biologic function of miR-4472 and its molecular mechanisms in cancer progression have not yet been reported.

MATERIALS AND METHODS

Real-time quantitative polymerase chain reaction was used to measure the expression of miR-4472 in breast cancer tissue and cell lines. The biologic functions of miR-4472 and its target gene were explored using Transwell, cell proliferation, and flow cytometry assays. Bioinformatics tools, dual-luciferase reporter assays, and Western blot were used to identify the target genes of miR-4472. Western blot was used to explain the participation of miR-4472 and target gene in epithelial-to-mesenchymal transition.

RESULTS

miR-4472 was significantly upregulated in highly metastatic breast cancer tissues, and its expression was positively associated with larger tumor size and advanced pTNM stage. miR-4472 promoted breast cancer cell metastasis and growth. Repulsive guidance molecule A (RGMA) was a direct target gene of miR-4472. RGMA was identified as a suppressor in cancer metastasis. miR-4472 downregulated expression of RGMA and promoted epithelial-to-mesenchymal transition by suppressing E-cadherin and initiating vimentin, β-catenin, and Slug.

CONCLUSIONS

miR-4472 contributes to the progression of breast cancer by regulating RGMA expression and inducing epithelial-to-mesenchymal transition, indicating that miR-4472/RGMA might serve as a therapeutic target for breast cancer.

circRNA and gastrointestinal cancer

Circular RNAs (circRNAs) are a novel class of endogenous noncoding RNAs that form covalently closed continuous loops without 3' end poly (A) tails and 5' end caps. circRNAs are more conservative and stable than linear RNA. circRNAs can specifically bind to microRNAs as competing endogenous RNA, thereby directly or indirectly regulating the expression of related genes. circRNAs have been implicated in several cancers including gastrointestinal (GI) cancers. Some circRNAs have the potential to become biological biomarkers and therapeutic targets of GI cancers. However, the multiple functional roles of circRNAs in GI cancers remain largely unclear.

High-throughput sequencing reveals circular RNA hsa_circ_0000592 as a novel player in the carcinogenesis of gastric carcinoma

Background/Aim: Gastric cancer is one of the most common malignant tumors, and its complex pathogenesis has not been fully elucidated. Circular RNAs (circRNAs) are involved in various biological processes and human diseases. However, their exact functional roles and mechanisms of action remain largely unclear. We previously discovered the differential expression of non-coding RNAs (ncRNAs) during the malignant transformation of human gastric epithelial cells. In this study, we investigated the functional roles of a significantly up-regulated circRNA (hsa_circ_0000592) in gastric cancer. Methods: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced malignant-transformed gastric epithelial cells (GES-1-T) and normal gastric epithelial cells (GES-1-N) were analyzed by high-throughput circRNA sequencing. The top 15 up-regulated circRNAs in high-throughput sequencing results were further confirmed by qRT-PCR in different gastric epithelial cell lines. The function of the most significant circRNA (hsa_circ_0000592) was investigated by using RNA interference (RNAi) assays, fluorescence in situ hybridization analysis (FISH), and bioinformatics prediction methods. Results: A total of 1509 genes were up-regulated and 3142 genes were down-regulated in GES-1-T cells when compared with GES-1-N cells. When compared with GES-1-N cells, hsa_circ_0000592 was obviously up-regulated in GES-1-T cells, as well as in other gastric cancer cell lines. The silencing of hsa_circ_0000592 mRNA led to a decrease in cell proliferation, cell cycle arrest at the G0/G1 phase, an increased rate of apoptosis, and a reduction in cell migration. Furthermore, FISH showed that hsa_circ_0000592 was mainly located in the cytoplasm, and a bioinformatics analysis suggested that hsa_circ_0000592 might function by sponging multiple miRNAs, and most notably four conserved miRNAs, including miR-139-3p, miR-200, miR-367-3p, and miR-33a-3p. Conclusion: This study is the first to identify hsa_circ_0000592 as a novel circRNA with a critical role in MNNG-induced gastric cancer. Due to the essential role of hsa_circ_0000592 in gastric carcinoma cells, it may be considered as a potential biomarker for use in diagnosing gastric carcinoma. Our findings provide a new insight into the function of circRNAs in environmental carcinogen-induced gastric cancer.

Deregulation of miRNA in Helicobacter pylori-Induced Gastric MALT Lymphoma: From Mice to Human

Gastric MALT lymphoma (GML) is directly caused by Helicobacter pylori infection but occurs only in a small number of infected subjects. Mechanisms underlying the initiation and progression of GML remain unclear. MicroRNAs (miRNAs) are small non-coding RNAs that are now considered as major players in inflammation and carcinogenesis, acting as oncogenes or tumor suppressors. Previous laboratory studies have shown in a GML mouse model that overexpression of a distinct set of five miRNAs (miR-21a, miR-135b, miR-142a, miR-150, miR-155) could play a critical role in the pathogenesis of GML. Our goal was to compare the miRNA expression profile obtained in the GML mouse model to that in human GML (11 cases of GML compared to 17 cases of gastritis control population). RTqPCR on the five dysregulated miRNAs in the GML mouse model and PCR array followed by RTqPCR confirmation showed that four miRNAs were up-regulated (miR-150, miR-155, miR-196a, miR-138) and two miRNAs down-regulated (miR-153, miR-7) in the stomachs of GML patients vs. gastritis control population. The analysis of their validated targets allowed us to postulate that these miRNAs (except miR-138) could act synergistically in a common signaling cascade promoting lymphomagenesis and could be involved in the pathogenesis of GML.

Upregulation of microRNA-7 contributes to inhibition of the growth and metastasis of osteosarcoma cells through the inhibition of IGF1R

We aim to uncover the methylation of microRNA-7 (miR-7) promoter in osteosarcoma (OS) and the inner mechanism of miR-7 on the progression of OS cells. Expression and methylation state of miR-7 in OS tissues and cells were detected. With the aim to unearth the ability of miR-7 in OS, the proliferation, cell cycle progression, apoptosis, invasion, migration of OS cells, and the tumor growth in nude mice were determined. Meanwhile, IGF1R expression was detected and the association between miR-7 and IGF1R was confirmed. The proliferating cell nuclear antigen (PCNA) expression was tested by immunohistochemical staining, and the lung metastasis was observed by H&E staining. miR-7 expression was decreased and methylation state of miR-7 was increased in OS tissues and cells. Upregulated miR-7 inhibited proliferation, cell cycle progression, invasion,and migration, while inducing apoptosis of OS cells and the tumor growth as well as PCNA expression in nude mice. Expression of IGF1R was downregulated in OS cells with overexpression of miR-7. Experiments verified the binding site between miR-7 and IGF1R. Our study demonstrates that abnormal methylation of miR-7 contributes to decreased miR-7 in OS. In addition, miR-7 represses the initiation and progression of OS cells through the inhibition of IGF1R.

miR-629-5p promotes growth and metastasis of hepatocellular carcinoma by activating β-catenin

Aberrant miR-629-5p expression in several cancer types has been reported. Nonetheless, its potential effect and mechanism of action on tumor growth and metastasis in hepatocellular carcinoma (HCC) have rarely been analyzed. In this study, we found that miR-629-5p was upregulated in HCC tissue samples as compared to matched adjacent-tissue samples. Overexpression of miR-629-5p promoted the proliferation, migration, and invasiveness of human HCC cells in vitro, whereas miR-629-5p knockdown reduced these parameters. Consistently, miR-629-5p overexpression accelerated tumor growth and metastasis in a nude mouse model. Mechanistically, miR-629-5p directly targeted the 3' untranslated region (3'UTR) of the secreted frizzled-related protein 2 (SFRP2) mRNA and suppressed its expression, resulting in the activation of β-catenin. Inhibition of β-catenin abrogated miR-629-5p-induced growth and invasiveness. Collectively, these results suggest that miR-629-5p activates β-catenin signaling by downregulating SFRP2 and thus promotes the growth and metastasis of HCC. These data open up new prospects for HCC treatment.

Deregulation of MicroRNA-375 Inhibits Proliferation and Migration in Gastric Cancer in Association With Autophagy-Mediated AKT/mTOR Signaling Pathways

Gastric cancer is a deadly disease. Some microRNAs are involved in tumor invasion and metastasis. Underexpression of miR-375 has been correlated with tumorigenesis, treatment resistance, and poor prognosis. In this study, we first analyzed the profiles and prognostic values of miR-375 expression in gastric cancer tissues from a public database, and the expression level of miR-375 in gastric cancer samples and gastric cancer cell lines was then analyzed by quantitative real- time polymerase chain reaction. Significant underexpression of miR-375 was seen in all the gastric cancer samples compared to paired paracarcinoma tissues, and the expression level of miR-375 in the gastric cancer cell lines was negatively associated with the cell migration ability. A Cell proliferation (CCK-8) assay was performed to examine cell viability. Overexpression of miR-375 suppressed the proliferation of gastric cancer cells. A Western blot analysis was carried out to test protein expression. Overexpression of miR-375 inhibited autophagy through the AKT/ mammalian target of rapamycin signaling pathway. MiR-375 regulated invasion and migration via AKT/ mammalian target of rapamycin pathway-mediated epithelial-to-mesenchymal transition. Wound healing and migration assays were used to determine the motility of gastric cancer cells. A gastric cancer xenograft nude mouse model was used for an in vivo efficacy evaluation. Overexpression of miR-375 significantly suppressed cell proliferation in the established gastric cancer xenograft nude mouse model. Our results demonstrate that increasing the expression level of miR-375 suppresses proliferation in vitro and in vivo, and they provide a mechanistic and applicable rationale for the future clinical evaluation of miR-375 in gastric cancer treatment. Our findings provide not only new information about the molecular mechanism of microRNAs in regulating invasion and migration in gastric cancer but also a theoretical principle for a potential targeted therapy for gastric cancer.

MicroRNA-7 as a potential therapeutic target for aberrant NF-κB-driven distant metastasis of gastric cancer

Background

Dysregulated miR-7 and aberrant NF-κB activation were reported in various human cancers. However, the expression profile, clinical relevance and dysregulated mechanism of miR-7 and NF-κB RelA/p65 in human gastric cancers (GC) metastasis remain largely unknown. This study is to investigate the expression profile, clinical relevance and dysregulated mechanism of miR-7 and NF-κB RelA/p65 in GC and to explore the potential therapeutic effect of miR-7 to GC distant metastasis.

Methods

TCGA STAD and NCBI GEO database were used to investigate the expression profile of miR-7 and NF-κB RelA/p65 and clinical relevance. Lentivirus-mediated gene delivery was applied to explore the therapeutic effect of miR-7 in GC. Real-time PCR, FACS, IHC, IF, reporter gene assay, IP, pre-miRNA-7 processing and binding assays were performed.

Results

Low miR-7 correlated with high RelA/p65 in GC with a clinical relevance that low miR-7 and high RelA/p65 as prognostic indicators of poor survival outcome of GC patients. Moreover, an impaired pre-miR-7 processing caused by dysregulated Dicer1 expression is associated with downregulated miR-7 in GC cells. Functionally, delivery of miR-7 displays therapeutic effects to GC lung and liver metastasis by alleviating hemangiogenesis, lymphangiogenesis as well as inflammation cells infiltration. Mechanistically, miR-7 suppresses NF-κB transcriptional activity and its downstream metastasis-related molecules Vimentin, ICAM-1, VCAM-1, MMP-2, MMP-9 and VEGF by reducing p65 and p-p65-ser536 expression. Pharmacologic prevention of NF-κB activator LPS obviously restored miR-7-suppressed NF-κB transcriptional activation and significantly reverted miR-7-inhibited cell migration and invasion.

Conclusions

Our data suggest loss of miR-7 in GC promotes p65-mediated aberrant NF-κB activation, facilitating GC metastasis and ultimately resulting in the worse clinical outcome. Thus, miR-7 may act as novel prognostic biomarker and potential therapeutic target for aberrant NF-κB-driven GC distant metastasis.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1074-6) contains supplementary material, which is available to authorized users.