Restoration of miR-7 expression suppresses the growth of Lewis lung cancer cells by modulating epidermal growth factor receptor signaling

Promoter A1312C mutation leads to microRNA-7 downregulation in human non-small cell lung cancer

MicroRNA-7 (miRNA-7, miR-7) is a unique class of tumor suppressors, plays an important role in various physiological and pathological processes including human non-small cell lung cancer (NSCLC). In previous works, we revealed that miR-7 could regulate the growth and metastasis of human NSCLC cells. However, the mechanism of dysregulated miR-7 expression in NSCLC remains to be further elucidated. In this study, based on clinical sample analysis, we found that the downregulated expression of miR-7 was dominantly attributed to the decreased level of pri-miR-7-2 in human NSCLC. Furthermore, there were four site mutations in the miR-7-2 promoter sequence. Notably, among these four sites, mutation at -1312 locus (A → C, termed as A1312C mutation) was dominate, and A1312C mutation further led to decreased expression of miR-7 in human NSCLC cells, accompanied with elevated transduction of NDUFA4/ERK/AKT signaling pathway. Mechanistically, homeobox A5 (HOXA5) is the key transcription factors regulating miR-7 expression in NSCLC. A1312C mutation impairs HOXA5 binding, thereby reducing the transcriptional activity of miR-7-2 promoter, resulting in downregulation of miR-7 expression. Together, these data may provide new insights into the dysregulation of specific miRNA expression in NSCLC and ultimately prove to be helpful in the diagnostic, prognostic, and therapeutic strategies against NSCLC.

Optimized thyroid transcription factor-1 core promoter-driven microRNA-7 expression effectively inhibits the growth of human non-small-cell lung cancer cells

Targeted gene therapy has become a promising approach for lung cancer treatment. In our previous work, we reported that the targeted expression of microRNA-7 (miR-7) operated by thyroid transcription factor-1 (TTF-1) promoter inhibited the growth of human lung cancer cells in vitro and in vivo; however, the intervention efficiency needed to be further improved. In this study, we identified the core promoter of TTF-1 (from -1299 bp to -871 bp) by 5' deletion assay and screened out the putative transcription factors nuclear factor-1 (NF-1) and activator protein-1 (AP-1). Further analysis revealed that the expression level of NF-1, but not AP-1, was positively connected with the activation of TTF-1 core promoter in human non-small-cell lung cancer (NSCLC) cells. Moreover, the silencing of NF-1 could reduce the expression level of miR-7 operated by TTF-1 core promoter. Of note, we optimized four distinct sequences to form additional NF-1-binding sites (TGGCA) in the sequence of TTF-1 core promoter (termed as ^optTTF-1 promoter), and verified the binding efficiency of NF-1 on the ^optTTF-1 promoter by electrophoretic mobility shift assay (EMSA). As expected, the ^optTTF-1 promoter could more effectively drive miR-7 expression and inhibit the growth of human NSCLC cells in vitro, accompanied by a reduced transduction of NADH dehydrogenase (ubiquinone) 1α subcomplex 4 (NDUFA4)/protein kinase B (Akt) pathway. Consistently, ^optTTF-1 promoter-driven miR-7 expression could also effectively abrogate the growth and metastasis of tumor cells in a murine xenograft model of human NSCLC. Finally, no significant changes were detected in the biological indicators or the histology of some important tissues and organs, including heart, liver, and spleen. On the whole, our study revealed that the optimized TTF-1 promoter could more effectively operate miR-7 to influence the growth of human NSCLC cells, providing a new basis for the development of microRNA-based targeting gene therapy against clinical lung cancer.

Long noncoding RNA BMPR1B-AS1 facilitates endometrial cancer cell proliferation and metastasis by sponging miR-7-2-3p to modulate the DCLK1/Akt/NF-κB pathway

Endometrial carcinoma (EC) originates from the endometrium and is one of the most common tumors in female patients, and its incidence has continued to increase in recent decades. LncRNAs are involved in the pathogenesis and metastasis of a variety of malignant tumors, which indicates that lncRNAs can be used as tumor diagnostic markers and potential therapeutic targets. In this study, we analyzed the RNA transcripts of EC cells from The Cancer Genome Atlas (TCGA) and first reported a novel lncRNA, BMPR1B-AS1, that was more highly expressed in endometrial cancer tissues than in adjacent tissues, and BMPR1B-AS1 could promote endometrial cancer cell proliferation and metastasis. Bioinformatics prediction and experimental results both suggested that BMPR1B-AS1 could modulate the malignant behaviors of endometrial cancer cell lines by sponging miR-7-2-3p to modulate DCLK1, and a DCLK1 inhibitor blocked the activation of the PI3K/Akt/NF-κB signaling pathway. Collectively, this study suggests that the BMPR1B-AS1/miR-7-2-3p/DCLK1 axis contributes to the proliferation and metastasis of endometrial cancer cells via the PI3K/Akt/NF-κB pathway.

Cell Behavior of Non-Small Cell Lung Cancer Is at EGFR and MicroRNAs Hands

Lung cancer is a complex disease associated with gene mutations, particularly mutations of Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) and epidermal growth factor receptor (EGFR). Non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) are the two major types of lung cancer. The former includes most lung cancers (85%) and are commonly associated with EGFR mutations. Several EGFR-tyrosine kinase inhibitors (EGFR-TKIs), including erlotinib, gefitinib, and osimertinib, are effective therapeutic agents in EGFR-mutated NSCLC. However, their effectiveness is limited by the development (acquired) or presence of intrinsic drug resistance. MicroRNAs (miRNAs) are key gene regulators that play a profound role in the development and outcomes for NSCLC via their role as oncogenes or oncosuppressors. The regulatory role of miRNA-dependent EGFR crosstalk depends on EGFR signaling pathway, including Rat Sarcoma/Rapidly Accelerated Fibrosarcoma/Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase 1/2 (Ras/Raf/MEK/ERK1/2), Signal Transducer and Activator of Transcription (STAT), Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells (NF-kB), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT), Janus kinase 1 (JAK1), and growth factor receptor-bound protein 2 (GRB2). Dysregulated expression of miRNAs affects sensitivity to treatment with EGFR-TKIs. Thus, abnormalities in miRNA-dependent EGFR crosstalk can be used as diagnostic and prognostic markers, as well as therapeutic targets in NSCLC. In this review, we present an overview of miRNA-dependent EGFR expression regulation, which modulates the behavior and progression of NSCLC.

Characteristics of circRNA and its approach as diagnostic tool in melanoma

One of the most common types of cancer in the world is skin cancer, which has been divided into two groups: non-melanoma and melanoma skin cancer. Different external and internal agents are considered as risk factors for melanoma skin cancer pathogenesis but the exact mechanisms are not yet confirmed. Genetic and epigenetic changes, UV exposure, arsenic compounds, and chemical substances are contributory factors to the development of melanoma. A correlation has emerged between new therapies and the discovery of a basic molecular pattern for skin cancer patients. Circular RNAs (circRNAs) are described as a unique group of extensively expressed endogenous regulatory RNAs with closed-loop structure bonds connecting the 5' and 3' ends, which are commonly expressed in mammalian cells. In this review, we describe the biogenesis of circular RNAs and its function in cancerous conditions focusing on the crosstalk between different circRNAs and melanoma. Increasing evidence suggests that circRNAs appears to be relative to the origin and development of skin-related diseases like malignant melanoma. Different circular RNAs like hsa_circ_0025039, hsa_circRNA006612, circRNA005537, and circANRIL, by targeting different cellular and molecular targets (e.g., CDK4, DAB2IP, ZEB1, miR-889, and let-7 c-3p), can participate in melanoma cancer progression.

Circular RNAs: new genetic tools in melanoma

Melanoma is the most lethal form of skin cancer. New technologies have resulted in major advances in the diagnosis and treatment of melanoma and other cancer types. Recently, some studies have investigated the role of circular RNAs (circRNAs) in different cancers. CircRNAs are a member of long noncoding RNA family mainly formed through back-splicing and have a closed-loop structure. These molecules affect several biological and oncogenic cascades in diverse ways via acting as microRNA sponge, interacting with RNA-binding proteins and acting as a transcription regulator. In this review, we made an insight into the impact of circRNA dysregulation in the melanoma tumorigenesis based on the presented evidences.

DWNN-RLS: regularized least squares method for predicting circRNA-disease associations

BACKGROUND

Many evidences have demonstrated that circRNAs (circular RNA) play important roles in controlling gene expression of human, mouse and nematode. More importantly, circRNAs are also involved in many diseases through fine tuning of post-transcriptional gene expression by sequestering the miRNAs which associate with diseases. Therefore, identifying the circRNA-disease associations is very appealing to comprehensively understand the mechanism, treatment and diagnose of diseases, yet challenging. As the complex mechanism between circRNAs and diseases, wet-lab experiments are expensive and time-consuming to discover novel circRNA-disease associations. Therefore, it is of dire need to employ the computational methods to discover novel circRNA-disease associations.

RESULT

In this study, we develop a method (DWNN-RLS) to predict circRNA-disease associations based on Regularized Least Squares of Kronecker product kernel. The similarity of circRNAs is computed from the Gaussian Interaction Profile(GIP) based on known circRNA-disease associations. In addition, the similarity of diseases is integrated by the mean of GIP similarity and sematic similarity which is computed by the direct acyclic graph (DAG) representation of diseases. The kernels of circRNA-disease pairs are constructed from the Kronecker product of the kernels of circRNAs and diseases. DWNN (decreasing weight k-nearest neighbor) method is adopted to calculate the initial relational score for new circRNAs and diseases. The Kronecker product kernel based regularised least squares approach is used to predict new circRNA-disease associations. We adopt 5-fold cross validation (5CV), 10-fold cross validation (10CV) and leave one out cross validation (LOOCV) to assess the prediction performance of our method, and compare it with other six competing methods (RLS-avg, RLS-Kron, NetLapRLS, KATZ, NBI, WP).

CONLUSION

The experiment results show that DWNN-RLS reaches the AUC values of 0.8854, 0.9205 and 0.9701 in 5CV, 10CV and LOOCV, respectively, which illustrates that DWNN-RLS is superior to the competing methods RLS-avg, RLS-Kron, NetLapRLS, KATZ, NBI, WP. In addition, case studies also show that DWNN-RLS is an effective method to predict new circRNA-disease associations.

Circular RNA ciRS-7 triggers the migration and invasion of esophageal squamous cell carcinoma via miR-7/KLF4 and NF-κB signals

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent and deadly cancers worldwide, especially in Eastern Asia. It has been indicated that circular RNAs (circRNA) are the key regulators in the development and progression of human cancers. We therefore evaluated the expression and regulation effects of ciRS-7 on the progression of ESCC, which is a recently identified circRNA and acts as a natural competing endogenous RNA. The expression of ciRS-7 was significantly increased in the ESCC tissues and cells as compared with their corresponding controls. In vitro study showed that ciRS-7 can promote the migration and invasion of ESCC cells. Over expression of miR-7, one of well-known targets of ciRS-7, can attenuate ciRS-7 induced invasion of ESCC cells and over expression of matrix metalloproteinase 2 (MMP2). The expression of stem cell marker Kruppel-like factor-4 (KLF-4), which has been reported as the target of miR7, increased significantly in ciRS-7 transfected ESCC cells. Knockdown of KLF-4 also attenuated over expression of ciRS-7 induced cell invasion. In addition, BAY 11-7082, the inhibitor of NF-κB, partially reversed ciRS-7 induced cell invasion. Mechanically studies indicated that ciRS-7 increased the expression of p65 via increasing the phosphorylation of IKK-α. Collectively, our present study revealed that ciRS-7 can trigger the migration and invasion of ESCC cells via miR-7/KLF4 and NF-κB signals. Targeted inhibition of ciRS-7 might be a potential approach for ESCC treatment.

Effects of Yangzheng Sanjie Decoction-containing serum mediated by microRNA-7 on cell proliferation and apoptosis in gastric cancer

Gastric cancer (GC) is one of the most common types of cancer and a leading cause of cancer-associated mortality. MicroRNAs (miRNAs/miRs) are demonstrated to function as oncomiRs or tumor-suppressor-miRs in GC. miR-7 has been identified to be a tumor suppressor of GC by targeting epidermal growth factor receptor (EGFR). In our previous study, Yangzheng Sanjie Decoction (YZSJD), a traditional Chinese formula, was identified to be effective in alleviating the symptoms and even postponing turnover of precancerous lesions. To elucidate the mechanism of YZSJD, the present study evaluated the effects of YZSJD of the GC MKN-45 cell line and investigated the underlying molecular mechanisms using YZSJD-containing serum (YCS). The expression of miR-7 in GC, normal and adjacent tissue samples was examined. The results demonstrated that YCS inhibited proliferation by inducing cell cycle arrest at the S phase, and significantly induced apoptosis compared with the control group. miR-7 was significantly downregulated in GC tissues compared with the matched ones. Using reverse transcription-quantitative polymerase chain reaction and western blot analysis, the expression of miR-7 was inversely associated with EGFR. This indicates that YCS inhibits proliferation and induces apoptosis of GC cells mediated by miR-7 targeting EGFR, which may be one of the mechanisms whereby YZSJD exerts its effects on GC.

The Circular RNA hsa_circ_0001445 Regulates the Proliferation and Migration of Hepatocellular Carcinoma and May Serve as a Diagnostic Biomarker

Circular RNAs (circRNA), a class of noncoding RNAs, have been found to be involved in various diseases. Here, the expression levels of the circRNA hsa_circ_0001445 in 73 pairs of hepatocellular carcinoma (HCC) and adjacent nontumor tissues were investigated by quantitative real-time polymerase chain reaction (qRT-PCR). Our data demonstrate that the hsa_circ_0001445 levels were significantly decreased in HCC tissues (P < 0.001) and markedly associated with the number of tumor foci (P = 0.014). Furthermore, in vitro approaches showed that overexpression of hsa_circ_0001445 promoted apoptosis and inhibited proliferation, migration, and invasion of HCC-derived cells, suggesting that hsa_circ_0001445 might be involved in the development of HCC. In addition, we found that the plasma hsa_circ_0001445 transcription levels in HCC patients were lower than those in cirrhosis (P < 0.001) and hepatitis B (P < 0.001) patients as well as in healthy controls (P < 0.001). In fact, receiver operating characteristic curve analysis indicated that plasma hsa_circ_0001445 could be a fairly accurate marker to distinguish HCC cases from healthy controls as well as patients with cirrhosis or hepatitis B.

Circular RNA: an emerging key player in RNA world

Insights into the circular RNA (circRNA) exploration have revealed that they are abundant in eukaryotic transcriptomes. Diverse genomic regions can generate different types of RNA circles, implying their diversity. Covalently closed loop structures elevate the stability of this new type of noncoding RNA. High-throughput sequencing analyses suggest that circRNAs exhibit tissue- and developmental-specific expression, indicating that they may play crucial roles in multiple cellular processes. Strikingly, several circRNAs could function as microRNA sponges and regulate gene transcription, highlighting a new class of important regulators. Here, we review the recent advances in knowledge of endogenous circRNA biogenesis, properties and functions. We further discuss the current findings about circRNAs in human diseases. In plants, the roles of circRNAs remain a mystery. Online resources and bioinformatics identification of circRNAs are essential for the analysis of circRNA biology, although different strategies yield divergent results. The understanding of circRNA functions remains limited; however, circRNAs are enriching the RNA world, acting as an emerging key player.

The understanding of circular RNAs as special triggers in carcinogenesis

Circular RNAs (circRNAs) are a large type of noncoding RNAs characterized by their circular shape resulting from covalently closed continuous loops. They are known to regulate gene expression in mammals. These tissue-specific transcripts are largely generated from exonic or intronic sequences of their host genes. Although several models of circRNA biogenesis have been proposed, the understanding of their origin is far from complete. Unlike other noncoding RNAs, circRNAs are widely expressed, highly conserved and stable in cytoplasm, which confer special functionalities to them. They are known to serve as microRNA (miRNA) sponges, regulators of alternative splicing, transcription factors and encode for proteins. The expression of circRNAs is associated with several pathological states and may potentially serve as novel diagnostic or predictive biomarkers. CircRNAs are known to regulate the expression of numerous cancer-related miRNAs. The circRNA-miRNA-mRNA axis is a known regulatory pattern of several cancer-associated pathways, with both agonist and antagonist effects on carcinogenesis. In consideration of their potential clinical relevance, circRNAs are at the center of ongoing research initiatives on cancer prevention and treatment. In this review, we discuss the current understanding of circRNAs and the prospects for their potential clinical application in the management of cancer patients.

Quantitative Proteomics Reveals the Regulatory Networks of Circular RNA CDR1as in Hepatocellular Carcinoma Cells

Circular RNAs (circRNAs), a class of widespread endogenous RNAs, play crucial roles in diverse biological processes and are potential biomarkers in diverse human diseases and cancers. Cerebellar-degeneration-related protein 1 antisense RNA (CDR1as), an oncogenic circRNA, is involved in human tumorigenesis and is dysregulated in hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying CDR1as functions in HCC remain unclear. Here we explored the functions of CDR1as and searched for CDR1as-regulated proteins in HCC cells. A quantitative proteomics strategy was employed to globally identify CDR1as-regulated proteins in HCC cells. In total, we identified 330 differentially expressed proteins (DEPs) upon enhanced CDR1as expression in HepG2 cells, indicating that they could be proteins regulated by CDR1as. Bioinformatic analysis revealed that many DEPs were involved in cell proliferation and the cell cycle. Further functional studies of epidermal growth factor receptor (EGFR) found that CDR1as exerts its effects on cell proliferation at least in part through the regulation of EGFR expression. We further confirmed that CDR1as could inhibit the expression of microRNA-7 (miR-7). EGFR is a validated target of miR-7; therefore, CDR1as may exert its function by regulating EGFR expression via targeting miR-7 in HCC cells. Taken together, we revealed novel functions and underlying mechanisms of CDR1as in HCC cells. This study serves as the first proteome-wide analysis of a circRNA-regulated protein in cells and provides a reliable and highly efficient method for globally identifying circRNA-regulated proteins.

CircRNA: a novel type of biomarker for cancer

Circular RNAs (circRNAs) are a class of long, non-coding RNAs molecules that shape a covalently closed continuous loop which have no 5'-3' polarity and contain no polyA tail. CircRNAs also possess relatively jarless framework and are highly tissue-specific expressed in the eukaryotic transcriptome. Emerging evidences have discovered that thousands of endogenous circRNAs are present in mammalian cells and they mediate gene expression at the transcriptional or post-transcriptional level by binding to microRNAs or other molecules and then inhibit their function. Similarly, increasing evidence indicates that circRNAs may play a role in the development of several types of diseases, including atherosclerotic vascular disease risk, neurological disorders, prion diseases, osteoarthritis and diabetes. Furthermore, circRNAs exhibit aberrant expression in multiform types of cancer, including colorectal cancer, hepatocellular carcinoma and pancreatic ductal adenocarcinoma. And based on the function of circRNAs in cancer, we believe that circRNAs may serve as diagnostic or tumor promising biomarkers. Moreover, it will provide a new therapeutic target for the treatment of cancer.

Curcumin exerts its antitumor activity through regulation of miR-7/Skp2/p21 in nasopharyngeal carcinoma cells

Curcumin, a natural polyphenol compound, exhibits tumor suppressive activity in a wide spectrum of cancers, including nasopharyngeal carcinoma cells. However, the exact molecular mechanisms governing this tumor suppressive activity remain elusive. Multiple studies have revealed that miRNAs are critically involved in tumorigenesis, indicating that targeting miRNAs could be a therapeutic strategy for treating human cancer. In the current study, we set out to determine whether curcumin regulates miR-7 expression in nasopharyngeal carcinoma cells. We found that curcumin inhibited cell growth, induced apoptosis, retarded cell migration and invasion, and triggered cell cycle arrest in the human nasopharyngeal carcinoma cell lines CNE1 and CNE2. Importantly, we observed that curcumin upregulated the expression of miR-7 and subsequently inhibited Skp2, a direct miR-7 target. Our results identified that upregulation of miR-7 by curcumin could benefit nasopharyngeal carcinoma patients.

Circular RNA ciRS-7-A Promising Prognostic Biomarker and a Potential Therapeutic Target in Colorectal Cancer

Purpose: Colorectal cancer is one of the most common malignancies worldwide. Recently, a novel circular RNA, ciRS-7, was proposed to be a potential miR-7 sponge. As miR-7, a putative tumor-suppressor, regulates the expression of several important drivers of colorectal cancer, we analyzed the clinical significance of ciRS-7 in colorectal cancer patients.Experimental Design: Initially, we evaluated the expression levels of ciRS-7 in a training cohort comprising of 153 primary colorectal cancer tissues and 44 matched normal mucosae. We subsequently confirmed its clinical relevance in an independent validation cohort (n = 165), and evaluated the effect of ciRS-7 on miR-7, and its target genes EGFR and RAF1. Functional analyses were performed in cell lines and an animal model to support clinical findings.Results: Our data revealed that ciRS-7 was significantly upregulated in colorectal cancer tissues compared with matched normal mucosae (P = 0.0018), and its overexpression was associated with poor patient survival (P = 0.0224 and 0.0061 in the training and validation cohorts, respectively). Multivariate survival analysis revealed that ciRS-7 emerged as an independent risk factor for overall survival (P = 0.0656 and 0.0324 in the training and validation cohorts, respectively). Overexpression of ciRS-7 in HCT116 and HT29 cells led to the blocking of miR-7 and resulted in a more aggressive oncogenic phenotype, and ciRS-7 overexpression permitted the inhibition of miR-7 and subsequent activation of EGFR and RAF1 oncogenes.Conclusions: CiRS-7 is a promising prognostic biomarker in colorectal cancer patients and may serve as a therapeutic target for reducing EGFR-RAF1 activity in colorectal cancer patients. Clin Cancer Res; 23(14); 3918-28. ©2017 AACR.

Targeted Expression of miR-7 Operated by TTF-1 Promoter Inhibited the Growth of Human Lung Cancer through the NDUFA4 Pathway

Targeted expression of gene technique is an important therapeutic strategy for lung cancer. MicroRNA-7 has been well documented as a promising tumor suppressor but never been test in specific gene-promoter-targeted expression in cancer gene therapy. Here, we first evaluated the efficacy of miR-7 expression operated by the promoter of TTF-1, a lineage-specific oncogene in lung cancer, in vitro using an eukaryotic vector of TTF-1-promoter-operated expression of miR-7 (termed as p-T-miR-7). Interestingly, using a nude mice model, the growth and metastasis of human lung cancer cells in vivo were significantly reduced in remote hypodermic injection of the p-T-miR-7 group, accompanied by increased expression of miR-7 and reduced transduction of the Akt and Erk pathway in situ. Mechanism aspect, global gene expression analysis showed that downregulation of NDUFA4, a novel target of miR-7, contributed to the effects of miR-7 expression operated by TTF-1 promoter on the growth and metastasis of human lung cancer cells, as well as altered transduction of the Akt and Erk pathway. Finally, there was no significant difference in weight or histopathology of other organs. These data provided a basis for development of novel modality of miRNA-based targeted expression therapy against clinical lung cancer.

Circular RNAs are miRNA sponges and can be used as a new class of biomarker

Circular RNAs (circRNAs) are a class of non-coding RNAs (ncRNAs) that are involved in transcriptional and posttranscriptional gene expression regulation. The development of deep sequencing of ribosomal RNA (rRNA)-depleted RNA libraries, associated with improved computational tools, has provided the identification of several new circRNAs in all sorts of organisms, from protists, plants and fungi to animals. Recently, it was discovered that endogenous circRNAs can work as microRNA (miRNA) sponges. This means that the circRNAs bind to miRNAs and consequently repress their function, providing a new model of action for this class of ncRNA, as well as indicating another mechanism that regulates miRNA activity. As miRNAs control a large set of biological processes, circRNA sponge activity will also affect these pathways. Several studies have associated miRNA sponges with human diseases, including osteoarthritis, diabetes, neurodegenerative pathologies and several types of cancer. Additionally, high stability, abundance and tissue-specific expression patterns make circRNA sponges very attractive for clinical research. Herein, we review the biogenesis, properties and function of endogenous circRNA sponges, with a special focus on those related to human cancer. A list of web tools available for the study of circRNAs is also given. Additionally, we discuss the possibility of using circRNAs as molecular markers for the diagnosis of diseases.

The circular RNA ciRS-7 (Cdr1as) acts as a risk factor of hepatic microvascular invasion in hepatocellular carcinoma

PURPOSE

Circular RNAs (circRNA) represent a novel class of widespread and diverse endogenous RNAs that regulate gene expression in mammals. microRNA-7 (miR-7) is a well-demonstrated suppressor of hepatocellular carcinoma (HCC). Recent studies have showed that one such circRNA, ciRS-7 (also termed as Cdr1as) was the inhibitor and sponge of miR-7 in the embryonic zebrafish midbrain and islet cells. However, the relationships among ciRS-7, miR-7 and clinical features of HCC remain to be clarified.

METHODS

Expression levels of ciRS-7, miR-7 and three miR-7-targeted mRNAs in 108 pairs of HCC and their matched non-tumor tissues were examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The protein production of these three miR-7-targeted mRNAs was further verified by Western blot. The relationship between ciRS-7 level and clinicopathological features as well as the recurrence of HCC patients was analyzed. The univariate and multivariate logistic regression analyses were used to detect the risk factors of hepatic microvascular invasion (MVI). The correlation among ciRS-7, miR-7 and miR-7-targeted mRNAs was evaluated using Spearman's correlation test.

RESULTS

There was no significant difference of ciRS-7 expression levels between the HCC tissues and the matched non-tumor tissues (0.67 ± 1.49 vs. 0.44 ± 0.45, p = 0.13), and the ciRS-7 levels in more than half of HCC tissues (65 out of 108, 60.2 %) were down-regulated when compared with their matched non-tumor tissues. However, the expression of ciRS-7 was significantly correlated with the following three clinicopathological characteristics of HCC patients: age <40 years (p = 0.02), serum AFP ≥400 ng/µl (p < 0.01) and hepatic MVI (p = 0.03). Meanwhile, up-regulated ciRS-7 expression was not only an independent risk factor of hepatic MVI but also had a capable predictive ability for MVI (AUC = 0.68, p = 0.001) at the cut-off value of 0.135. Furthermore, the expression of ciRS-7 in HCC tissues with concurrent MVI was inversely correlated with that of miR-7 (r = -0.39, p = 0.007) and positively related with that of two miR-7-targeted genes [PIK3CD (r = 0.55, p < 0.001) and p70S6K (r = 0.34, p = 0.021)]. In addition, the median recurrent time of patients from higher ciRS-7 level group was shorter than that of lower ciRS-7 group (18 vs. 25 months), but no significant difference was observed (p = 0.38).

CONCLUSIONS

The expression levels of ciRS-7 were comparable between HCC and matched non-tumor tissues. However, the highly ciRS-7 expression in HCC tissues was significantly correlated with hepatic MVI, AFP level and younger age and thus partly related with the deterioration of HCC. Especially, ciRS-7 was one of the independent factors of hepatic MVI. These data suggested that ciRS-7 may be a promising biomarker of hepatic MVI and a novel therapy target for restraining MVI.

Inhibition of miR-7 promotes angiogenesis in human umbilical vein endothelial cells by upregulating VEGF via KLF4

Recent lentiviral-based microRNA (miRNA) library screening has identified miRNA-7 (miR-7) as an anti‑angiogenic miRNA in human umbilical vein endothelial cells (HUVECs). However, the underlying mechanism of miR-7 in the suppression of angiogenesis remains largely unknown. In the present study, we report that miR-7 inhibition promoted angiogenesis by upregulating vascular endothelial growth factor (VEGF) and directly targeting Krüppel-like factor 4 (KLF4). Downregulation of miR-7 promoted tube formation of HUVECs, accompanied by upregulation of mRNA and protein levels of both VEGF and KLF4. miR-7 directly targeted KLF4 as demonstrated by luciferase reporter assay and miR-7 mimics decreased KLF4. Furthermore, bioinformatic analysis revealed the presence of multiple DNA-binding elements of KLF4 in the VEGF promoter. Chromatin immunoprecipitation (ChIP) demonstrated that the KLF4 antibody specifically pulled down the VEGF promoter in the HUVECs. Furthermore, ectopic overexpression of KLF4 induced VEGF mRNA and protein levels. In addition, KLF4 silencing inhibited the angiogenesis induced by the miR-7 inhibitor in the HUVECs. Our results demonstrated that KLF4 is a direct target of miR-7 and a transcription activator of VEGF. These findings indicate that the miR-7-KLF4-VEGF signaling axis plays an important role in the regulation of angiogenesis in HUVECs, suggesting that miR-7 is a potential agent for the development of anti-angiogenic therapeutics in vascular diseases and solid tumors.

Role of microRNA-7 in digestive system malignancy

There are several malignancies of the digestive system (including gastric, pancreatic and colorectal cancers, and hepatocellular carcinoma), which are the most common types of cancer and a major cause of death worldwide. MicroRNA (miR)-7 is abundant in the pancreas, playing an important role in pancreatic development and endocrine function. Expression of miR-7 is downregulated in digestive system malignancies compared with normal tissue. Although there are contrasting results for miR-7 expression, almost all research reveals that miR-7 is a tumor suppressor, by targeting various genes in specific pathways. Moreover, miR-7 can target different genes simultaneously in different malignancies of the digestive system. By acting on many cytokines, miR-7 is also involved in many gastrointestinal inflammatory diseases as a significant carcinogenic factor. Consequently, miR-7 might be a biomarker or therapeutic target gene in digestive system malignancies.

MicroRNA-7: a promising new target in cancer therapy

The incidence of tumors with life-threatening effects has increased gradually over time; however, the mechanisms involved in tumor development have not been fully elucidated. Recent studies have shown that microRNA-7 (miR-7), which is endogenous non-coding RNA molecules of approximately 23 nucleotides, plays an important role in the occurrence and development of tumors as a key tumor suppressor. Mechanistic evidence showed that miR-7 is closely related to the growth, metastasis, and prognosis of various malignant tumors through regulating different target molecules, which suggest that miR-7 may be a new target for the clinical diagnosis and treatment of various tumors. In this review, we summarize current knowledge of the relationship between miR-7 and tumor development, diagnosis, and treatment.

microRNA deregulation in keloids: an opportunity for clinical intervention?

Keloids are defined as benign dermal scars invading adjacent healthy tissue, characterized by aberrant fibroblast dynamics and overproduction of extracellular matrix. However, the aetiology and molecular mechanism of keloid production remain poorly understood. Recent discoveries have shed new light on the involvement of a class of non-coding RNAs known as microRNAs (miRNA), in keloid formation. A number of miRNAs have differential expression in keloid tissues and keloid-derived fibroblasts. These miRNAs have been characterized as novel regulators of cellular processes pertinent to wound healing, including extracellular matrix deposition and fibroblast proliferation. Delineating the functional significance of miRNA deregulation may help us better understand pathogenesis of keloids, and promote development of miRNA-directed therapeutics against this condition.

MicroRNA-203 induces apoptosis by upregulating Puma expression in colon and lung cancer cells

The present study investigated the relationship between microRNA-203 (miR-203) and the p53 upregulated modulator of apoptosis (Puma) in colon (HCT116) and lung cancer (A549) cells. Colon and lung cancer cell lines were selected for this study since a relationship between p53/miR-203 and p53/Puma has been established in both cancers. In the present study, adriamycin and nutlin-3 were used to activate p53, which induced both miR-203 and Puma expression in HCT116 cells. In contrast, HCT 116 cells with downregulated p53 showed decreased miR-203 and Puma expression. Importantly, we found that overexpressed miR-203 in HCT116 cells resulted in significantly increased Puma expression (P<0.05). Based on these findings, we hypothesized that another limb of the p53/Puma axis depends on miR-203 expression. To further validate this relationship, we used lung cancer cells (A549) and found that activated p53 increased both miR-203 and Puma expression. In addition, we found that Puma expression remained elevated in cells with overexpressed miR-203 in the presence of p53 downregulation. Cumulatively, our data purport that p53 not only increased Puma expression directly, but that it may also do so through miR-203. Additionally, functional studies revealed that miR-203 overexpression induced apoptosis and inhibited cell invasiveness.

Promoter mutation of tumor suppressor microRNA-7 is associated with poor prognosis of lung cancer

The significance of promoter mutations of microRNAs (miRNAs) in lung cancer is poorly understood. Recent evidence demonstrated that miRNA-7 (miR-7), a unique member of the miRNA family, exhibited decreased expression and has emerged as an important regulator in lung tumorigenesis. However, the mechanism underlying the downregulation of miR-7 in lung cancer remains largely unknown. In this study, we investigated the sites of mutation of the miR-7 promoter in lung cancer tissues using DNA sequencing. We identified a G→C change at the -617 site (25/39, 64.1%) and an A→G change at the -604 site (20/39, 51.3%) in the miR-7 promoter region in lung cancer tissues. Moreover, the expression of miR-7 in cancer tissue with promoter site mutations was lower compared with that in cancer tissue without mutations (P<0.05). Furthermore, we demonstrated that mutations at these sites may decrease the activity of the miR-7 promoter and alter the expression of miR-7. Notably, mutations at these sites of the miR-7 promoter were found to be closely associated with poor prognosis of lung cancer patients (P=0.037). These data may provide novel insight on the altered expression of specific miRNA molecules in lung cancer and ultimately prove to be helpful in the development of prognostic and therapeutic strategies against lung cancer.

Clinical Potential of microRNA-7 in Cancer

microRNAs (miRNAs) are a family of short, non-coding RNA molecules that drive a complex network of post-transcriptional gene regulation by enhancing target mRNA decay and/or inhibiting protein synthesis from mRNA transcripts. They regulate genes involved in key aspects of normal cell growth, development and the maintenance of body homeostasis and have been closely linked to the development and progression of human disease, in particular cancer. Over recent years there has been much interest regarding their potential as biomarkers and as therapeutic agents or targets. microRNA-7 (miR-7) is a 23 nucleotide (nt) miRNA known primarily to act as a tumour suppressor. miR-7 directly inhibits a number of oncogenic targets and impedes various aspects of cancer progression in vitro and in vivo, however, some studies have also implicated miR-7 in oncogenic roles. This review summarises the role of miR-7 in cancer, its potential in miRNA-based replacement therapy and its capacity as both a diagnostic and prognostic biomarker.

Emerging Roles of MicroRNAs in EGFR-Targeted Therapies for Lung Cancer

Lung cancer is a leading cause of cancer mortality worldwide. Several molecular pathways underlying mechanisms of this disease have been partly elucidated, among which the epidermal growth factor receptor (EGFR) pathway is one of the well-known signaling cascades that plays a critical role in tumorigenesis. Dysregulation of the EGFR signaling is frequently found in lung cancer. The strategies to effectively inhibit EGFR signaling pathway have been mounted for developing anticancer therapeutic agents. However, most anti-EGFR-targeted agents fail to repress cancer progression because of developing drug-resistance. Therefore, studies of the mechanisms underpinning the resistance toward anti-EGFR agents may provide important findings for lung cancer treatment using anti-EGFR therapies. Recently, increasing numbers of miRNAs are correlated with the drug resistance of lung cancer cells to anti-EGFR agents, indicating that miRNAs may serve as novel targets and/or promising predictive biomarkers for anti-EGFR therapy. In this paper, we summarize the emerging role of miRNAs as regulators to modulate the EGFR signaling and the resistance of lung cancer cells to anti-EGFR therapy. We also highlight the evidence supporting the use of miRNAs as biomarkers for response to anti-EGFR agents and as novel therapeutic targets to circumvent the resistance of lung cancer cells to EGFR inhibitors.

MicroR-545 enhanced radiosensitivity via suppressing Ku70 expression in Lewis lung carcinoma xenograft model

Objective

Radiotherapy is an important therapeutic method for lung cancer. However, in clinical situations, cellular resistance to radiotherapy is a significant component of tumor treatment failure. Thus, clarification in cellular mechanism underlying radiosensitivity of cancer cell is urgently needed. In this study, we established a radiation model of Lewis lung carcinoma in C57BL/6 mice and investigated the possible signaling molecule involved in this process.

Methods

C57BL/6 mice were subcutaneously transplanted with Lewis lung carcinoma cells and locally irradiated followed by measurement in tumor volume. Levels of miR-545 and Ku70 mRNA expression were determined by using Quantitative Real-Time PCR. Expression of Ku70 was determined by using western blot assay. Cell viability was analyzed by MTT assay. Cell apoptosis was examined by using TUNEL assay.

Results

In mice bearing Lewis lung carcinoma tumor, local radiotherapy suppressed tumor growth as well as enhanced expression of miR-545 and downregulated Ku70 level. Inhibition of miR-545 expression reduced radiosensitivity of Lewis tumor. In vitro Lewis lung carcinoma cells experiment, we observed that miR-545 regulated Ku70 expression by targeting Ku70 3′UTR and this process was involved in radiotherapy. This was demonstrated by result of cell proliferation assay in which irradiation reduced apoptosis of cells was mediated by miR-545 inactivation which was reversed by Ku70 silence.

Conclusion

miR-545 increased radiosensitivity of Lewis lung carcinoma via inhibiting Ku70 expression.

The emerging landscape of circular RNA ciRS-7 in cancer (Review)

Circular RNAs (circRNAs) are a novel class of non-coding RNA molecules ubiquitously present in the cytoplasm of eukaryotic cells. CircRNAs are generated from exons or introns via multiple mechanisms. A recently identified circRNA, ciRS-7, can regulate the activities of miRNAs, mRNAs, and RBP to exert specific biological effects. Also, ciRS-7 acts as a natural competing endogenous RNA, a.k.a. 'super sponge' of microRNA-7 (miR-7) that sequesters and competitively inhibits the activity of miR-7. This competition between ciRS-7 and miR-7 may have profound effects on oncogenesis. This review will summarize the origin and functions of ciRS-7 and discuss the relationship among ciRS-7, its target molecules and cancer.

Expression and significance of circulating microRNA-31 in lung cancer patients

Background

The aim of this study was to investigate the expression level of circulating microRNA-31(miRNA-31) in lung cancer patients and its clinical significance.

Material/Methods

Real-time fluorescent quantitative PCR was utilized to detect the circulating miRNA-31 expression levels in 300 lung cancer patients and 300 health control subjects. The ROC curve was drawn to evaluate the diagnostic value of the circulating miRNA-31 expression levels in lung cancer. The 300 lung cancer patients were divided into a miRNA-31 low-expression group and a miRNA-31 high-expression group. A survival curve was drawn according to the Kaplan-Meier method to evaluate the prognostic value of the circulating microRNA-31 expression levels for lung cancer.

Results

The circulating miRNA-31 expression levels in the lung cancer patients (l.88±0. 67) increased significantly (P<0.001) compared to the healthy controls (0.58±0. 44). The area under the ROC curve drawn according to the circulating miRNA-31 expression levels was 0.785 (95% CI=0.486–0.763). When the critical value was 1.27, the sensitivity and specificity for lung cancer diagnosis according to the circulating miRNA-31 expression levels were 0.769 and 0.745, respectively. The difference in the survival curve between the miRNA-31 low-expression group (123 cases) and high-expression group (177 cases) was statistically significant (P=0.004). Median survival period of the low-expression group (38.44 months) was longer than that of the high-expression group (25.23 months).

Conclusions

miRNA-31 may be a molecular marker for the diagnostic and prognostic evaluation of primary lung cancer.