Long noncoding RNA CCAT1, which could be activated by c-Myc, promotes the progression of gastric carcinoma

HOTAIR, a long non-coding RNA driver of malignancy whose expression is activated by FOXC1, negatively regulates miRNA-1 in hepatocellular carcinoma

Evidence is rapidly accumulating that long non-coding RNAs (lncRNAs) are involved in human tumorigenesis and are dysregulated in multiple cancers, including hepatocellular carcinoma (HCC). lncRNAs can regulate essential pathways that contribute to tumor initiation and progression with tissue specificity, which suggests that lncRNAs may be valuable biomarkers and therapeutic targets. HOX transcript antisense intergenic RNA (HOTAIR) has previously been demonstrated to be an oncogene and a negative prognostic factor in a variety of cancers; however, the factors that contribute to the upregulation of HOTAIR and the interaction between HOTAIR and microRNAs (miRNAs or miRs) are largely unknown. In the present study, the expression levels of HOTAIR, forkhead box C1 (FOXC1) and miRNA-1 were examined in 50 matched pairs of HCC and HCC cells. The effects of HOTAIR on HCC cell proliferation were tested using trypan blue exclusion assay. The effect of HOTAIR on HCC growth in vivo was determined in a (nu/nu) mouse model. A computational screening of HOTAIR promoter was conducted to search for transcription factor-binding sites. FOXC1 binding to the promoter region of HOTAIR was confirmed using a chromatin immunoprecipitation assay. A search for miRNAs that had complementary base paring with HOTAIR was performed utilizing an online software program. The interaction between miR-1 and HOTAIR was examined using a luciferase reporter assay. Gain and loss of function approaches were used to determine the changes of HOTAIR or miR-1 expression. The relative levels of FOXC1 and HOTAIR expression in HCC tissues and HepG2 cells were significantly higher than those in normal liver LO2 cells and adjacent carcinoma tissues; the relative expression of miR-1 exhibited the opposite pattern. Overexpression of HOTAIR promoted HCC cell proliferation and progression of tumor xenografts. The present authors have demonstrated that FOXC1 binds to the upstream region of HOTAIR in HCC cells and that FOXC1 activates lncRNA HOTAIR expression in HCC HepG2 cells, which suggests that HOTAIR harbors a miRNA-1 binding site. The present data revealed that this binding site is vital for the regulation of miRNA-1 by HOTAIR. Furthermore, HOTAIR negatively regulated the expression of miRNA-1 in HepG2 cells. Additionally, the present study demonstrated that the oncogenic activity of HOTAIR is in part based on the negative regulation of miR-1. Taken together, these results suggest that HOTAIR is a FOXC1-activated driver of malignancy, which acts in part through the repression of miR-1.

Current Status of Long Non-Coding RNAs in Human Breast Cancer

Breast cancer represents a major health burden in Europe and North America, as recently published data report breast cancer as the second leading cause of cancer related death in women worldwide. Breast cancer is regarded as a highly heterogeneous disease in terms of clinical course and biological behavior and can be divided into several molecular subtypes, with different prognosis and treatment responses. The discovery of numerous non-coding RNAs has dramatically changed our understanding of cell biology, especially the pathophysiology of cancer. Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts >200 nucleotides in length. Several studies have demonstrated their role as key regulators of gene expression, cell biology and carcinogenesis. Deregulated expression levels of lncRNAs have been observed in various types of cancers including breast cancer. lncRNAs are involved in cancer initiation, progression, and metastases. In this review, we summarize the recent literature to highlight the current status of this class of long non-coding lncRNAs in breast cancer.

Epigenetic silencing of miR-218 by the lncRNA CCAT1, acting via BMI1, promotes an altered cell cycle transition in the malignant transformation of HBE cells induced by cigarette smoke extract

Cigarette smoking is the strongest risk factor for the development of lung cancer, the leading cause of cancer-related deaths. However, the molecular mechanisms leading to lung cancer are largely unknown. A long-noncoding RNA (lncRNA), CCAT1, regarded as cancer-associated, has been investigated extensively. Moreover, the molecular mechanisms of lncRNAs in regulation of microRNAs (miRNAs) induced by cigarette smoke remain unclear. In the present investigation, cigarette smoke extract (CSE) caused an altered cell cycle and increased CCAT1 levels and decreased miR-218 levels in human bronchial epithelial (HBE) cells. Depletion of CCAT1 attenuated the CSE-induced decreases of miR-218 levels, suggesting that miR-218 is negatively regulated by CCAT1 in HBE cells exposed to CSE. The CSE-induced increases of BMI1 levels and blocked by CCAT1 siRNA were attenuated by an miR-218 inhibitor. Moreover, in CSE-transformed HBE cells, the CSE-induced cell cycle changes and elevated neoplastic capacity were reversed by CCAT1 siRNA or BMI1 siRNA. This epigenetic silencing of miR-218 by CCAT1 induces an altered cell cycle transition through BMI1 and provides a new mechanism for CSE-induced lung carcinogenesis.

Long Noncoding RNAs in Lung Cancer

Despite great progress in research and treatment options, lung cancer remains the leading cause of cancer-related deaths worldwide. Oncogenic driver mutations in protein-encoding genes were defined and allow for personalized therapies based on genetic diagnoses. Nonetheless, diagnosis of lung cancer mostly occurs at late stages, and chronic treatment is followed by a fast onset of chemoresistance. Hence, there is an urgent need for reliable biomarkers and alternative treatment options. With the era of whole genome and transcriptome sequencing technologies, long noncoding RNAs emerged as a novel class of versatile, functional RNA molecules. Although for most of them the mechanism of action remains to be defined, accumulating evidence confirms their involvement in various aspects of lung tumorigenesis. They are functional on the epigenetic, transcriptional, and posttranscriptional level and are regulators of pathophysiological key pathways including cell growth, apoptosis, and metastasis. Long noncoding RNAs are gaining increasing attention as potential biomarkers and a novel class of druggable molecules. It has become clear that we are only beginning to understand the complexity of tumorigenic processes. The clinical integration of long noncoding RNAs in terms of prognostic and predictive biomarker signatures and additional cancer targets could provide a chance to increase the therapeutic benefit. Here, we review the current knowledge about the expression, regulation, biological function, and clinical relevance of long noncoding RNAs in lung cancer.

Transcriptome profiling of lncRNA and co-expression networks in esophageal squamous cell carcinoma by RNA sequencing

Long non-coding RNAs (lncRNAs) are emerging as crucial regulators of cancer. To identify novel targets for further study in esophageal squamous cell carcinoma (ESCC), we performed a genome-wide analysis of lncRNA expression in 12 ESCC tumor and normal tissues. Publicly available RNA-seq data were downloaded from the NCBI, GEO, and Co-LncRNA databases, and lncRNA and messenger RNA (mRNA) expression profiles were analyzed. In total, 127 lncRNAs were found to be differentially expressed, with a greater than fourfold change in ESCC tumor tissues compared with normal tissues. Among these lncRNAs, 98 were upregulated and 29 downregulated. Moreover, 1469 network nodes and 1720 connection edges between 119 lncRNAs and 1350 coding genes were integrated into the lncRNA and mRNA co-expression network. Bioinformatic analysis using GO terms revealed that these dysregulated lncRNAs are associated with developmental processes, proteinaceous extracellular matrix, and protein binding activity, with ECM-receptor interaction and the PI3K-Akt signaling pathway enrichment. Lastly, qRT-PCR results verified two significantly upregulated lncRNAs and three significantly downregulated lncRNAs in 50 pairs of ESCC tissues and adjacent normal tissues. These results reveal the landscape of ESCC-associated lncRNAs and co-expression networks, providing important insight regarding the lncRNAs involved in ESCC.

Exploring the role of molecular biomarkers as a potential weapon against gastric cancer: A review of the literature

Gastric cancer (GC) is a global health problem and a major cause of cancer-related death with high recurrence rates ranging from 25% to 40% for GC patients staging II-IV. Unfortunately, while the majority of GC patients usually present with advanced tumor stage; there is still limited evidence-based therapeutic options. Current approach to GC management consists mainly of; endoscopy followed by, gastrectomy and chemotherapy or chemo-radiotherapy. Recent studies in GC have confirmed that it is a heterogeneous disease. Many molecular characterization studies have been performed in GC. Recent discoveries of the molecular pathways underlying the disease have opened the door to more personalized treatment and better predictable outcome. The identification of molecular markers is a useful tool for clinical managementin GC patients, assisting in diagnosis, evaluation of response to treatment and development of novel therapeutic modalities. While chemotherapeutic agents have certain physiological effects on the tumor cells, the prediction of the response is different from one type of tumor to the other. The specificity of molecular biomarkers is a principal feature driving their application in anticancer therapies. Here we are trying to focus on the role of molecular pathways of GC and well-established molecular markers that can guide the therapeutic management.

Long noncoding RNAs in digestive system cancers: Functional roles, molecular mechanisms, and clinical implications (Review)

Long noncoding RNAs (lncRNAs) are emerging as new players in various diseases including cancer. LncRNAs have been shown to play multifaceted roles in the development, progression, and metastasis of cancer. In this review, we highlight the lncRNAs that are critically involved in the pathogenesis of digestive system cancers (DSCs). We summarize the roles of the lncRNAs in DSCs and the underlying mechanisms responsible for their functions. The DSC-associated lncRNAs interact with a wide spectrum of molecules to regulate gene expression at transcriptional, post-transcriptional, and translational levels. We also provide new insights into the clinical significance of these lncRNAs, which are found to be closely associated with the aggressiveness of DSCs and could predict the prognosis of DSC patients. Moreover, lncRNAs have been suggested as promising therapeutic targets in DSCs. Therefore, better understanding of the functional roles of lncRNAs will provide new biomarkers for DSC diagnosis, prognosis, and therapy.

Urothelial cancer associated 1: a long noncoding RNA with a crucial role in cancer

BACKGROUND

Urothelial cancer associated 1 (UCA1) is a long noncoding RNA (lncRNA) which has gained more attention in recent years due to its aberrant expression in embryogenesis and a broad range of cancer tissues and cells. Importantly, multiple studies have shown that UCA1 plays oncogenic roles in tumor growth and metastasis, and it may act as a potential biomarker and therapeutic target for human cancers. However, the molecular mechanism of UCA1 in cancer initiation, progression and metastasis remains incompletely understood. Thus, gaining a better understanding of the functional mechanism of UCA1 in cancer onset and progression is of the utmost significance for evaluating the potential application of UCA1.

RESULTS AND DISCUSSION

In this review, we discuss UCA1 expression profiling, isoform, expression regulation, biological role and mechanism for UCA1 tumor-promoting effect. We further discuss the potential clinical application of UCA1 as a promising diagnostic biomarker or therapeutic target for human cancers.

CONCLUSION

UCA1 functions as an oncogenic lncRNA in several malignancies, and it might become a potential biomarker or therapeutic target for human cancers.

LncRNA GClnc1 Promotes Gastric Carcinogenesis and May Act as a Modular Scaffold of WDR5 and KAT2A Complexes to Specify the Histone Modification Pattern

Long noncoding RNAs (lncRNA) play a role in carcinogenesis. However, the function of lncRNAs in human gastric cancer remains largely unknown. In this study, we identified a novel lncRNA, GClnc1, which was upregulated and associated with tumorigenesis, tumor size, metastasis, and poor prognosis in gastric cancer. GClnc1 affected gastric cancer cell proliferation, invasiveness, and metastasis in multiple gastric cancer models. Mechanistically, GClnc1 bound WDR5 (a key component of histone methyltransferase complex) and KAT2A histone acetyltransferase, acted as a modular scaffold of WDR5 and KAT2A complexes, coordinated their localization, specified the histone modification pattern on the target genes, including SOD2, and consequently altered gastric cancer cell biology. Thus, GClnc1 is mechanistically, functionally, and clinically oncogenic in gastric cancer. Targeting GClnc1 and its pathway may be meaningful for treating patients with gastric cancer.

SIGNIFICANCE

This report documents a novel lncRNA, GClnc1, which may act as a scaffold to recruit the WDR5 and KAT2A complex and modify the transcription of target genes. This study reveals that GClnc1 is an oncogenic lncRNA in human gastric cancer. Cancer Discov; 6(7); 784-801. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 681.

CCAT1: a pivotal oncogenic long non-coding RNA in human cancers

Long non-coding RNAs (lncRNAs) compose a group of non-protein-coding RNAs - more than 200 nucleotides in length. Recent studies have shown that lncRNAs play important roles in different cellular processes, including proliferation, differentiation, migration and invasion. Deregulation of lncRNAs has been widely reported in human tumours, in which they are able to function as either oncogenes (on the one hand) or tumour suppressor genes (on the other). Deregulation of CCAT1 (colon cancer-associated transcript-1), an oncogenic lncRNA, has been documented in different types of malignancy, such as gastric cancer, colorectal cancer and hepatocellular carcinoma. In this regard, enforced expression of CCAT1 exerts potent tumorigenic effects by promoting cell proliferation, invasion and migration. Recent evidence has also shown that CCAT1 may serve as a prognostic cancer biomarker. In this review, we provide an overview of current evidence relating to the role and biological function of CCAT1 in tumour development.

Long Non-Coding RNA CCAT1 Acts as a Competing Endogenous RNA to Regulate Cell Growth and Differentiation in Acute Myeloid Leukemia

Long non-coding RNAs (lncRNAs) are involved in multiple cellular events, as well as in tumorigenesis. Colon cancer-associated transcript-1 (CCAT1) gene encodes an lncRNA whose over-activation was observed in an expanding list of primary human solid tumors and tumor cell lines, however its biological roles in acute myeloid leukaemia (AML) has not been reported yet at present. In this study, the aberrant upregulation of CCAT1 was detected in French-American-British M4 and M5 subtypes of adult AML patients. By gain- and loss-of-function analysis, we determined that CCAT1 repressed monocytic differentiation and promoted cell growth of HL-60 by sequestering tumor suppressive miR-155. Accordingly, a significant decrease in miR-155 level was detected in AML patients. Re-introduction of miR-155 into HL-60 cells restored monocytic maturation and repressed cell proliferation. Furthermore, CCAT1 could up-regulated c-Myc via its competing endogenous RNA (ceRNA) activity on miR-155. In conclusion, these results revealed new mechanism of lncRNA CCAT1 in AML development, and suggested that the manipulation of CCAT1 expression could serve as a potential strategy in AML therapy.

The insights of Let-7 miRNAs in oncogenesis and stem cell potency

The ability of the classic tumour‐suppressive let‐7 family to inhibit carcinogenesis, tumour progression, recurrence and pluripotency of cancer stem cells has generated significant interest in the field of cancer research. Through suppressing and degrading downstream‐targeted mRNAs, let‐7 affected most aspects of cell biology. It is perplexing how let‐7 affects oncogenesis, as the large influx of new miRNAs and other kinds of non‐coding RNAs are continuously defined. In this review, we delineate the complex functions of let‐7 and discuss the future direction of let‐7 research.

Long Non-Coding RNA lincRNA-ROR Promotes the Progression of Colon Cancer and Holds Prognostic Value by Associating with miR-145

Large intergenic non-coding RNA ribonucleic acids-ROR (lincRNA-ROR) has been reported to exert impacts on the maintenance of induced pluripotent stem cells and embryonic stem cells, and play important roles in human hepatocellular cancer. It contributes to tumorigenesis and metastasis and functions as a competing endogenous RNA (ceRNA) by sponging miR-145 in breast cancer. However, its clinical significance and prognostic value in colon cancer remain unknown. The aim of the present study was to clarify the clinicopathological role and prognostic value of lincRNA-ROR and miR-145 in colon cancer. In the present study, qRT-PCR was performed to measure the expression levels of lincRNA-ROR in colon cancer tissues and cell lines. Then, the clinicopathological significance and prognostic value of lincRNA-ROR were analyzed. LincRNA-ROR expression correlated with pT stage, pN stage, AJCC stage and vascular invasion. Knockdown of lincRNA-ROR restored the expression of miR-145, and had a significant influence on colon cancer cell proliferation, migration and invasion. Patients of the high lincRNA-ROR/low miR-145 group had significantly poorer outcomes than those of the low lincRNA-ROR/high miR-145 group. Taken together, Overexpression of lincRNA-ROR combined with depletion of miR-145 may exert crucial impact on colon cancer prognosis evaluation and treatment.

LncRNA BCAR4 wires up signaling transduction in breast cancer

Long noncoding RNAs (lncRNAs) are dysregulated in many cancer types and are believed to play crucial roles in regulating several hallmarks of cancer biology. Currently, most studies support the concept that lncRNAs are involved in either transcriptional or post-transcriptional processes via binding/targeting epigenetic modifiers or hRNP complexes. The discovery of new biological functions of lncRNA and novel RNA binding proteins suggests that lncRNAs may be implicated in a broad spectrum of biological processes such as signal transduction, allosteric regulation of cytoplasmic enzymatic activities, among other potential processes. In a recent report that we have made, based on open-ended lncRNA pulldown technology and a series of systematic analyses, we suggest that lncRNAs also play critical roles in the regulation of noncanonical Hedgehog/GLI 2 signal transduction pathways in cancer cells, which further broadens the scope of known lncRNA functions and aids in the discovery and design of more effective and evidence-based therapeutic targets for the treatment of human cancers and other diseases.

Long non-coding RNA CASC11 interacts with hnRNP-K and activates the WNT/β-catenin pathway to promote growth and metastasis in colorectal cancer

The abnormal expression of many long non-coding RNAs (lncRNAs) has been reported in the progression of various tumors, and these lncRNAs can be useful as diagnostic indicators and anti-tumor targets. Therefore, it is important to identify lncRNAs that can be used for the clinical prevention and treatment of colorectal cancer (CRC). Here, we report that cancer susceptibility candidate 11 (CASC11) was upregulated in CRC tissues; increased CASC11 expression in CRC was associated with tumor size, serosal invasion, lymph metastasis, and the tumor-node-metastasis (TNM) stage. Functional experiments showed that CASC11 can promote CRC cell proliferation and metastasis in vitro and in vivo. Furthermore, CASC11 can target heterogeneous ribonucleoprotein K (hnRNP-K) to activate WNT/β-catenin signaling in CRC cells. In addition, we found that c-Myc directly bound to the promoter regions of CASC11 and increased promoter histone acetylation to enhance CASC11 expression. Together, our findings indicate that the novel lncRNA CASC11 may serve as a candidate diagnostic biomarker and a promising therapeutic target for CRC.

Long noncoding RNA SNHG1 predicts a poor prognosis and promotes hepatocellular carcinoma tumorigenesis

Hepatocellular carcinoma (HCC) is the main cause of cancer mortality worldwide. Its poor prognosis is mainly ascribed to high recurrence rate. Identifying novel prognostic biomarkers and therapeutic targets would be vital for HCC management. Long noncoding RNA (lncRNA) is a class of RNA with various roles in tumorigenesis. The aim of this study was to investigate the clinical significance and functions of lncRNA-small nucleolar RNA host gene 1 (SNHG1) in HCC. In this study, we found SNHG1 was upregulated in HCC tissues in comparison with adjacent liver tissues in both publicly available microarray data and our own cohort. High SNHG1 expression was correlated with large tumor size, poor differentiation, and aggressive BCLC stage. Kaplan-Meier survival analysis demonstrated that high SNHG1 expression predicts poor prognosis of HCC patients. Gain-of-function and loss-of function experiments showed that SNHG1 promotes HCC cells proliferation, cell cycle progression, and inhibits HCC cells apoptosis. Further experiments revealed that SNHG1 promotes HCC cells proliferation through inhibiting p53 and p53-target genes expression. Collectively, our results demonstrated the clinical prognostic significance and roles of SNHG1 in HCC, and suggested that SNHG1 may be considered as a prognostic biomarker and therapeutic target for HCC.

From junk to master regulators of invasion: lncRNA functions in migration, EMT and metastasis

Metastasis is a multistep process that involves the dissemination of cells from the primary tumor and colonization of distant secondary organs. Epithelial cells at the invasive front of a carcinoma acquire an enhanced migratory phenotype in a process called epithelial-to-mesenchymal transition (EMT). This cellular plasticity seems to drive the initiation of metastasis. Identifying important molecules and understanding their molecular mechanisms is a key to cancer prognosis and the development of therapeutics for late stage malignancies. Recent advances in sequencing technology uncovered that the mammalian genome is pervasively transcribed into many nonprotein-coding RNAs including the class of long noncoding RNA, a.k.a. lncRNA. Several lncRNAs are differentially expressed in carcinomas and they are emerging as potent regulators of tumor progression and metastasis. Here, we review the diverse molecular mechanisms, cellular roles and regulatory patterns that are becoming apparent for the noncoding transcriptome. Chromatin modification, epigenetic regulation, alternative splicing and translational control by MALAT1, HOTAIR and TRE lncRNAs represent important examples of lncRNA-mediated control of cell migration and invasion, EMT and metastasis. Beyond these better characterized examples, numerous additional transcripts have been associated with cancer metastasis, but their functional roles await their discovery.

A novel long noncoding RNA-LOWEG is low expressed in gastric cancer and acts as a tumor suppressor by inhibiting cell invasion

PURPOSE

Long noncoding RNA (lncRNA) have been reported to be involved in the development of multiple cancers. The aim of this study was to report the identification of lncRNA-CTD-2108O9.1, which we have named lncRNA low expressed in gastric cancer (lncRNA-LOWEG), and investigate its role in cancer development.

METHODS

Total RNA was extracted from the tissues of 94 patients with GC, one normal gastric epithelial cell line and four GC cell lines. Expression levels of lncRNA-LOWEG were determined by real-time PCR. Moreover, CCK-8 proliferation assay, transwell cell invasion assay and flow cytometry were performed to study the effects of lncRNA-LOWEG on SGC-7901 cell proliferation, cell invasion and cell cycle progression. Lastly, western blot and real-time PCR were used to verify the potential target genes of lncRNA-LOWEG.

RESULTS

Significantly reduced expression of lncRNA-LOWEG was found in gastric cancer tissues and cell lines (SGC-7901, AGS, BGC-823 and HG-27) compared with patient-matched nontumorous adjacent tissues (P < 0.01) or the normal gastric cell line GES-1 (P < 0.05). Moreover, the transwell assay showed that the number of cells capable of passing through the Matrigel was significantly reduced after lncRNA-LOWEG transfection (P < 0.05). However, lncRNA-LOWEG overexpression did not significantly influence cell proliferation (P > 0.05) and cell cycle progression (P > 0.05). Lastly, western blot and real-time PCR analysis suggested that lncRNA-LOWEG is positively correlated with the expression of leukemia inhibitory factor receptor (LIFR) gene at the translational level.

CONCLUSIONS

LncRNA-LOWEG is a tumor suppressor that inhibits GC cell invasion. And LIFR gene is up-regulated by lncRNA-LOWEG.

Long noncoding RNAs in gastric cancer: functions and clinical applications

Over the last two decades, genome-wide studies have revealed that only a small fraction of the human genome encodes proteins; long noncoding RNAs (lncRNAs) account for 98% of the total genome. These RNA molecules, which are >200 nt in length, play important roles in diverse biological processes, including the immune response, stem cell pluripotency, cell proliferation, apoptosis, differentiation, invasion, and metastasis by regulating gene expression at the epigenetic, transcriptional, and posttranscriptional levels. However, the detailed molecular mechanisms underlying lncRNA function are only partially understood. Recent studies showed that many lncRNAs are aberrantly expressed in gastric cancer (GC) tissues, gastric juice, plasma, and cells, and these alterations are linked to the occurrence, progression, and outcome of GC. Here, we review the current knowledge of the biological functions and clinical aspects of lncRNAs in GC.

The long noncoding RNA colon cancer-associated transcript-1/miR-490 axis regulates gastric cancer cell migration by targeting hnRNPA1

Colon cancer-associated transcript-1 (CCAT1) is a highly conserved long noncoding RNA that is deregulated in several cancers. However, its role in gastric carcinoma and its post-transcriptional regulation remain poorly understood. In this study, we provide the first evidence that CCAT1 regulates miR-490 in gastric cancer (GC) cells. Interestingly, miR-490 can also repress CCAT1 expression. CCAT1 expression was significantly upregulated, and miR-490 expression was downregulated in GC. The negative correlation between miR-490 and CCAT1 expression was observed in GC tissues. Importantly, CCAT1 contains a putative miR-490-binding site, and deletion of this binding site abolishes their miR-490 responsiveness. Post-transcriptional CCAT1 silencing by miR-490 significantly suppressed GC cell migration. Furthermore, miR-490 directly bound to the hnRNPA1 mRNA 3'-UTR to repress its translation. Inhibition of miR-490 rescued CCAT1 siRNA-mediated suppression of cell migration. hnRNPA1 expression was significantly upregulated in GC specimens, and there was a negative correlation between miR-490 and hnRNPA1 expression and also a positive correlation between hnRNAP1 expression level and CCAT1 level. Taken together, we show for the first time that the CCAT1/miR-490/hnRNPA1 axis promotes GC migration, and it may have a possible diagnostic and therapeutic potential in GC.

Emerging roles of non-coding RNAs in gastric cancer: Pathogenesis and clinical implications

Gastric cancer is a leading cause of cancer-related deaths. However, the mechanisms underlying gastric carcinogenesis remain largely unclear. The association of non-coding RNAs (ncRNAs) with cancer has been widely studied during the past decade. In general, ncRNAs have been classified as small ncRNAs, including microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). Emerging evidence shows that miRNAs and lncRNAs play key roles in the formation and progression of many cancers. In this review, we focus on the regulation of miRNAs and lncRNAs in gastric cancer. miRNAs and lncRNAs appear to be involved in gastric tumor growth, invasion, and metastasis and in establishment of the gastric tumor microenvironment through various mechanisms. Furthermore, we also discuss the possibilities of establishing miRNAs and lncRNAs as potential biomarkers and therapeutic targets for gastric cancer. Taken together, we summarize the emerging roles of ncRNAs in gastric cancer development and their possible clinical significance.

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

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

Cancer RNA-Seq Nexus: a database of phenotype-specific transcriptome profiling in cancer cells

The genome-wide transcriptome profiling of cancerous and normal tissue samples can provide insights into the molecular mechanisms of cancer initiation and progression. RNA Sequencing (RNA-Seq) is a revolutionary tool that has been used extensively in cancer research. However, no existing RNA-Seq database provides all of the following features: (i) large-scale and comprehensive data archives and analyses, including coding-transcript profiling, long non-coding RNA (lncRNA) profiling and coexpression networks; (ii) phenotype-oriented data organization and searching and (iii) the visualization of expression profiles, differential expression and regulatory networks. We have constructed the first public database that meets these criteria, the Cancer RNA-Seq Nexus (CRN, http://syslab4.nchu.edu.tw/CRN). CRN has a user-friendly web interface designed to facilitate cancer research and personalized medicine. It is an open resource for intuitive data exploration, providing coding-transcript/lncRNA expression profiles to support researchers generating new hypotheses in cancer research and personalized medicine.

Long noncoding RNA MIR31HG exhibits oncogenic property in pancreatic ductal adenocarcinoma and is negatively regulated by miR-193b

Long noncoding RNAs (lncRNAs) play important regulatory roles in a variety of diseases, including many tumors. However, the functional roles of these transcripts and mechanisms responsible for their deregulation in pancreatic ductal adenocarcinoma (PDAC) are not thoroughly understood. In this study, we discovered that lncRNA MIR31HG is markedly upregulated in PDAC. Knockdown of MIR31HG significantly suppressed PDAC cell growth, induced apoptosis and G1/S arrest, and inhibited invasion, whereas enhanced expression of MIR31HG had the opposite effects. Online database analysis tools showed that miR-193b could target MIR31HG and we found an inverse correlation between MIR31HG and miR-193b in PDAC specimens. Inhibition of miR-193b expression significantly upregulated the MIR31HG level, while overexpression of miR-193b suppressed MIR31HG's expression and function, suggesting that MIR31HG is negatively regulated by miR-193b. Moreover, using luciferase reporter and RIP assays, we provide evidence that miR-193b directly targeted MIR31HG by binding to two microRNA binding sites in the MIR31HG sequence. On the other hand, MIR31HG may act as an endogenous 'sponge' by competing for miR-193b binding to regulate the miRNA targets. Collectively, these results demonstrate that MIR31HG functions as an oncogenic lncRNA that promotes tumor progression, and miR-193b targets not only protein-coding genes but also the lncRNA, MIR31HG.

Non-coding landscapes of colorectal cancer

For two decades Vogelstein’s model has been the paradigm for describing the sequence of molecular changes within protein-coding genes that would lead to overt colorectal cancer (CRC). This model is now too simplistic in the light of recent studies, which have shown that our genome is pervasively transcribed in RNAs other than mRNAs, denominated non-coding RNAs (ncRNAs). The discovery that mutations in genes encoding these RNAs [i.e., microRNAs (miRNAs), long non-coding RNAs, and circular RNAs] are causally involved in cancer phenotypes has profoundly modified our vision of tumour molecular genetics and pathobiology. By exploiting a wide range of different mechanisms, ncRNAs control fundamental cellular processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis: these data have also confirmed their role as oncogenes or tumor suppressors in cancer development and progression. The existence of a sophisticated RNA-based regulatory system, which dictates the correct functioning of protein-coding networks, has relevant biological and biomedical consequences. Different miRNAs involved in neoplastic and degenerative diseases exhibit potential predictive and prognostic properties. Furthermore, the key roles of ncRNAs make them very attractive targets for innovative therapeutic approaches. Several recent reports have shown that ncRNAs can be secreted by cells into the extracellular environment (i.e., blood and other body fluids): this suggests the existence of extracellular signalling mechanisms, which may be exploited by cells in physiology and pathology. In this review, we will summarize the most relevant issues on the involvement of cellular and extracellular ncRNAs in disease. We will then specifically describe their involvement in CRC pathobiology and their translational applications to CRC diagnosis, prognosis and therapy.

Dysregulation of non-coding RNAs in gastric cancer

Gastric cancer (GC) is one of the most common cancers in the world and a significant threat to the health of patients, especially those from China and Japan. The prognosis for patients with late stage GC receiving the standard of care treatment, including surgery, chemotherapy and radiotherapy, remains poor. Developing novel treatment strategies, identifying new molecules for targeted therapy, and devising screening techniques to detect this cancer in its early stages are needed for GC patients. The discovery of non-coding RNAs (ncRNAs), primarily microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), helped to elucidate the mechanisms of tumorigenesis, diagnosis and treatment of GC. Recently, significant research has been conducted on non-coding RNAs and how the regulatory dysfunction of these RNAs impacts the tumorigenesis of GC. In this study, we review papers published in the last five years concerning the dysregulation of non-coding RNAs, especially miRNAs and lncRNAs, in GC. We summarize instances of aberrant expression of the ncRNAs in GC and their effect on survival-related events, including cell cycle regulation, AKT signaling, apoptosis and drug resistance. Additionally, we evaluate how ncRNA dysregulation affects the metastatic process, including the epithelial-mesenchymal transition, stem cells, transcription factor activity, and oncogene and tumor suppressor expression. Lastly, we determine how ncRNAs affect angiogenesis in the microenvironment of GC. We further discuss the use of ncRNAs as potential biomarkers for use in clinical screening, early diagnosis and prognosis of GC. At present, no ideal ncRNAs have been identified as targets for the treatment of GC.

Increased urothelial cancer associated 1 is associated with tumor proliferation and metastasis and predicts poor prognosis in colorectal cancer

Long non-coding RNA, urothelial cancer associated 1 (UCA1), is reported to play a critical role in progression of carcinogenesis. In the present study, we identified differential expression of UCA1 in colorectal cancer (CRC) and paired peritumoral tissues using gene expression microarray analyses. qPCR analysis confirmed that UCA1 was upregulated in CRC (p<0.001) and the expression of UCA1 was statistically correlated with lymph node metastasis (P=0.040), distant metastasis (P=0.043) and tumor stage (P=0.010). Kaplan-Meier analysis indicated that patients with high UCA1 expression had a poor prognosis. Moreover, multivariate analysis identified UCA1 overexpression as an independent predictor for CRC. We also found that knockdown of UCA1 significantly suppressed cell proliferation and metastasis in CRC cells. Flow cytometry assays showed UCA1 silencing induced G0/G1 growth arrest and apoptosis of CRC cells. To further investigate the regulatory mechanisms of UCA1, we identified that Ets-2 bound to the UCA1 core promoter using luciferase assays. Collectively, our findings suggested that UCA1 might be an important prognostic indicator in CRC and may be a potential target for diagnosis and gene therapy.

Roles of competing endogenous RNAs in gastric cancer

Long noncoding RNA (lncRNA) is >200 nucleotides long and lacks coding ability. LncRNA was regarded as transcript noise, until emerging results showed its roles in development, homeostasis and carcinogenesis. LncRNAs containing microRNA (miRNA) response elements could compete with the miRNA target gene and regulate its expression through decreasing free functional miRNA. Such lncRNA is called competing endogenous RNA (ceRNA), and the 'lncRNA-miRNA' interaction appreciably enriches the world of RNA-RNA regulation. Gastric cancer involves dysregulation of both protein-coding genes and noncoding genes, and the ceRNA regulatory mechanism may participate in this pathogenic process. In this review, we discuss recent findings on the roles of ceRNAs in gastric carcinogenesis.

Long Noncoding RNAs as New Architects in Cancer Epigenetics, Prognostic Biomarkers, and Potential Therapeutic Targets

Recent advances in genome-wide analysis have revealed that 66% of the genome is actively transcribed into noncoding RNAs (ncRNAs) while less than 2% of the sequences encode proteins. Among ncRNAs, high-resolution microarray and massively parallel sequencing technologies have identified long ncRNAs (>200 nucleotides) that lack coding protein function. LncRNAs abundance, nuclear location, and diversity allow them to create in association with protein interactome, a complex regulatory network orchestrating cellular phenotypic plasticity via modulation of all levels of protein-coding gene expression. Whereas lncRNAs biological functions and mechanisms of action are still not fully understood, accumulating data suggest that lncRNAs deregulation is pivotal in cancer initiation and progression and metastatic spread through various mechanisms, including epigenetic effectors, alternative splicing, and microRNA-like molecules. Mounting data suggest that several lncRNAs expression profiles in malignant tumors are associated with prognosis and they can be detected in biological fluids. In this review, we will briefly discuss characteristics and functions of lncRNAs, their role in carcinogenesis, and their potential usefulness as diagnosis and prognosis biomarkers and novel therapeutic targets.

LncRNAs: emerging biomarkers in gastric cancer

Long noncoding RNAs (lncRNAs) recently have been recognized as having a critical role in cancer development and progression. Gastric cancer remains a major clinical challenge worldwide owing to poor prognosis and limited treatment options. Accumulating studies have demonstrated that lncRNAs may play an active role in tumorigenesis, metastasis, prognosis and drug resistance of gastric cancer. Here, we collect recent knowledge to show differential expression of lncRNA in gastric cancer and their underlying mechanism of activities in gastric cancer involved in epigenetic, transcription and post-transcriptional processing. This review focuses on the regulation and function of gastric cancer-related lncRNAs and provides an overview of current effects to exploit them to be potential biomarkers and therapeutic targets for gastric cancer.

Using gastric juice lncRNA-ABHD11-AS1 as a novel type of biomarker in the screening of gastric cancer

Long noncoding RNAs (lncRNAs) play vital roles in tumorigenesis. However, the diagnostic values of most lncRNAs are largely unknown. To investigate whether gastric juice lncRNA-ABHD11-AS1 can be a potential biomarker in the screening of gastric cancer, 173 tissue samples and 130 gastric juice from benign lesion, gastric dysplasia, gastric premalignant lesions, and gastric cancer were collected. ABHD11-AS1 levels were detected by reverse transcription-polymerase chain reaction. Then, the relationships between ABHD11-AS1 levels and clinicopathological factors of patients with gastric cancer were investigated. The results showed that ABHD11-AS1 levels in gastric cancer tissues were significantly higher than those in other tissues. Its levels in gastric juice from gastric cancer patients were not only significantly higher than those from cases of normal mucosa or minimal gastritis, atrophic gastritis, and gastric ulcers but also associated with gender, tumor size, tumor stage, Lauren type, and blood carcinoembryonic antigen (CEA) levels. More importantly, when using gastric juice ABHD11-AS1 as a marker, the positive detection rate of early gastric cancer patients was reached to 71.4 %. Thanks to the special origin of gastric juice, these results indicate that gastric juice ABHD11-AS1 may be a potential biomarker in the screening of gastric cancer.

Expression and regulation of long non-coding RNAs in colorectal cancer

Long non-coding RNA (lncRNA) has a messenger RNA-like structure, greater than 200 nucleotides in length, and extensively existing in both the cytoplasm and nucleus. However, almost all lncRNAs cannot be transcribed into proteins. Increasing studies showed that lncRNAs participate in many eukaryotic activities, such as regulating the expression of genes at epigenetic, transcriptional and post-transcriptional levels, and regulating human growth and development, and also, cell apoptosis. Their aberrant expression is involved in many human diseases and tumorigenesis. This article reviews the latest results of lncRNAs in colorectal cancer with regards to their expression and regulation.

The long noncoding RNA regulation at the MYC locus

Aberrant expression of long noncoding RNAs (lncRNAs) has been linked to cancers. The MYC oncoprotein is a key contributor to the development of many human tumors. Recent studies have revealed that a number of lncRNAs originating from the human 8q24 locus previously known to corresponding to a 'gene desert' are transcribed and play important roles in MYC regulation. In this review, we highlight recent progress in how these lncRNAs participate in control of MYC levels in normal and tumor cells.

Long noncoding RNA-LET, which is repressed by EZH2, inhibits cell proliferation and induces apoptosis of nasopharyngeal carcinoma cell

Recent studies have reported that long noncoding RNAs (lncRNAs) play critical roles in carcinogenesis and progression. LncRNA-LET, a recently identified lncRNA, has been shown to be a tumor suppressor in hepatocellular carcinoma. However, the expression and functional of lncRNA-LET in other type of cancers remain largely unknown. In this study, we found that lncRNA-LET was significantly downregulated in nasopharyngeal carcinoma (NPC) tissues compared with corresponding normal tissues. Decreased LET expression is significantly correlated with advanced clinical stage, larger tumor size, increased lymph node tumor burden, and poor survival of NPC patients. Gain- and loss-of-function experiments demonstrated that enhanced LET expression inhibited NPC cells proliferation and induced cell apoptosis. By contrast, the knockdown of LET promoted NPC cells proliferation and inhibited cell apoptosis. Importantly, we found lncRNA-LET is transcriptional repressed by EZH2-mediated H3K27 histone methylation on the LET promoter. The expressions of EZH2 and lncRNA-LET are significantly inversely correlated in NPC tissues. Collectively, these findings indicate a pivotal role for lncRNA-LET in NPC cell proliferation and apoptosis, and reveal an epigenetic mechanism for lncRNA-LET dysregulation.

Antisense Long Noncoding RNA HIF1A-AS2 Is Upregulated in Gastric Cancer and Associated with Poor Prognosis

BACKGROUND

Long noncoding RNAs (lncRNAs) have been recently shown to play important regulatory roles in fundamental biological processes, and many of them are deregulated in several human cancers. LncRNA hypoxia-inducible factor 1alpha antisense RNA-2 (HIF1A-AS2) is overexpressed in nonpapillary clear-cell renal carcinomas and involved in cancer progression.

AIM

This study was to evaluate the expression of HIF1A-AS2 in gastric cancer (GC) and further explore its biological function in GC cells.

MATERIALS AND METHODS

Quantitative real-time polymerase chain reaction was used to detect the expression level of HIF1A-AS2 in GC tissues. The correlation of its expression with clinicopathological features was analyzed. Area under receiver operating characteristic curve (ROC(AUC)) was constructed to evaluate the diagnostic value of HIF1A-AS2. Besides, tumor cell proliferation was assessed following knockdown of HIF1A-AS2, by MTT and colony formation assay in vitro, and tumor formation assay in a nude mouse model in vivo.

RESULTS

The expression of HIF1A-AS2 was upregulated in GC tumorous tissues compared with the adjacent normal tissues (P < 0.001). Its overexpression was correlated with TNM stages (P = 0.008), tumor invasion (P = 0.016), lymph node metastasis (P = 0.042), and poor prognosis (P = 0.001). In addition, ROC(AUC) of HIF1A-AS2 was up to 0.673 (95 % CI 0.596-0.744, P < 0.001). Moreover, knockdown of HIF1A-AS2 expression by siRNA could inhibit cell proliferation in vitro and tumorigenesis in vivo.

CONCLUSIONS

HIF1A-AS2 is overexpressed in GC and may play a pivotal role in tumor cell proliferation. It can be used as a potential diagnostic and prognostic biomarker for GC.

Roles of long non-coding RNAs in gastric cancer metastasis

Gastric cancer is the second leading cause of cancer-related deaths. Metastasis, which is an important element of gastric cancer, leads to a high mortality rate and to a poor prognosis. Gastric cancer metastasis has a complex progression that involves multiple biological processes. The comprehensive mechanisms of metastasis remain unclear, though traditional regulation modulates the molecular functions associated with metastasis. Long non-coding RNAs (lncRNAs) have a role in different gene regulatory pathways by epigenetic modification and by transcriptional and post-transcription regulation. lncRNAs participate in various diseases, including Alzheimer’s disease, cardiovascular disease, and cancer. The altered expressions of certain lncRNAs are linked to gastric cancer metastasis and invasion, as with tumor suppressor genes or oncogenes. Studies have partly elucidated the roles of lncRNAs as biomarkers and in therapies, as well as their gene regulatory mechanisms. However, comprehensive knowledge regarding the functional mechanisms of gene regulation in metastatic gastric cancer remains scarce. To provide a theoretical basis for therapeutic intervention in metastatic gastric cancer, we reviewed the functions of lncRNAs and their regulatory roles in gastric cancer metastasis.

Long Noncoding RNAs in Digestive System Malignancies: A Novel Class of Cancer Biomarkers and Therapeutic Targets?

High throughput methodologies have revealed the existence of an unexpectedly large number of long noncoding RNAs (lncRNAs). The unconventional role of lncRNAs in gene expression regulation and their broad implication in oncogenic and tumor suppressive pathways have introduced lncRNAs as novel biological tumor markers. The most prominent example of lncRNAs application in routine clinical practice is PCA3, a FDA-approved biomarker for prostate cancer. Regarding digestive system malignancies, the oncogenic HOTAIR is one of the most widely studied lncRNAs in the preclinical level and has already been identified as a potent prognostic marker for major malignancies of the gastrointestinal tract. Here, we provide an overview of recent findings regarding the emerging role of lncRNAs not only as key regulators of cancer initiation and progression in colon, stomach, pancreatic, liver, and esophageal cancers, but also as reliable tumor markers and therapeutic tools. lncRNAs can be easily, rapidly, and cost-effectively determined in tissues, serum, and gastric juice, making them highly versatile analytes. Taking also into consideration the largely unmet clinical need for early diagnosis and more accurate prognostic/predictive markers for gastrointestinal cancer patients, we comment upon the perspectives of lncRNAs as efficient molecular tools that could aid in the clinical management.

A FOXM1 related long non-coding RNA contributes to gastric cancer cell migration

Long non-coding RNAs (LncRNAs) have been reported that play important roles in the progression and metastasis of some carcinomas. In the present study, we identified a new LncRNA, FRLnc1, from a microarray analysis in which those LncRNAs were regulated by FOXM1, an oncogene widely studied in most malignancies. Quantitative real-time PCR (qRT-PCR) results in gastric cancer cell lines indicated FRLnc1 expression is positively correlated with FOXM1 level, supporting the microarray data. Furthermore, the RNA level of FRLnc1 is upregulated in 49% (20/41) of cancer samples compared with neighboring non-cancerous stomach tissues. The in vitro functional analyses demonstrated that FRLnc1 knockdown by RNA interference suppressed cell migration in MGC803 and AGS cells, whereas FRLnc1 overexpression promoted cell migration in BGC823 and SGC7901 cells. Moreover, FRLnc1 could enhance the distant metastasis of SGC7901 cells by tail vein injection approach in mice. We also identified TGFβ1 and Twist as the downstream effectors of FRLnc1 in the regulation of cell migration by qRT-PCR analysis. Taken together, our findings suggest that FRLnc1 is involved in gastric cancer cell migration and for the first time set up the link between FOXM1 and LncRNA in cancer.

Reciprocal repression between TUSC7 and miR-23b in gastric cancer

Recently, long noncoding RNAs (lncRNAs) were demonstrated to play important regulatory roles in biological processes and cancer biology. However, the overall pathophysiological contribution of lncRNAs to gastric cancer (GC) remains largely unknown. In this study, differentially expressed lncRNAs in GC and paired adjacent normal tissue samples were identified by microarray and were validated using quantitative real-time polymerase chain reaction (qRT-PCR). One particular lncRNA, tumour suppressor candidate 7 (TUSC7), was analyzed in sequential large cohorts, and the Kaplan-Meier method with the log-rank test for comparisons was used to analyse the survival data. The results indicated that TUSC7 was downregulated in GC samples and was an independent prognostic indicator of disease-free survival (DFS) and disease-specific survival (DSS) in GC patients. Applying loss-of-function and gain-of-function approaches, we determined that TUSC7 suppressed tumour cell growth in vitro and in vivo. Furthermore, we showed that TUSC7 was a direct transcriptional target of p53 via interaction of p53 with the putative p53-response element in the upstream region of TUSC7. Finally, we demonstrated reciprocal repression between TUSC7 and miR-23b; in contrast to TUSC7, miR-23b promoted cell growth. The results indicated that TUSC7 is a p53-regulated tumour suppressor that acts in part by repressing miR-23b and that TUSC7 may be a key regulatory hub in GC.

The functional role of long non-coding RNA in digestive system carcinomas

In recent years, long non-coding RNAs (lncRNAs) are emerging as either oncogenes or tumor suppressor genes. Recent evidences suggest that lncRNAs play a very important role in digestive system carcinomas. However, the biological function of lncRNAs in the vast majority of digestive system carcinomas remains unclear. Recently, increasing studies has begun to explore their molecular mechanisms and regulatory networks that they are implicated in tumorigenesis. In this review, we highlight the emerging functional role of lncRNAs in digestive system carcinomas. It is becoming clear that lncRNAs will be exciting and potentially useful for diagnosis and treatment of digestive system carcinomas, some of these lncRNAs might function as both diagnostic markers and the treatment targets of digestive system carcinomas.

Overexpression of eukaryotic translation initiation factor 5A2 (EIF5A2) correlates with cell aggressiveness and poor survival in gastric cancer

Eukaryotic translation initiation factor 5A2 (EIF5A2) plays an important role in tumor progression and prognosis evaluation. However, little information is available about its potential role in gastric cancer. This study aimed to investigate the function of EIF5A2 in tumor progression and its potential mechanisms. EIF5A2 expression was measured in human gastric cancer cell lines, the immortalized gastric mucosal epithelial cell line (GES-1) and human gastric cancer tissues and knocked down by RNA interference or upregulated by EIF5A2 plasmid transfection. Cell proliferation, migration and invasion were assessed in vitro. The downstream targets of EIF5A2 were examined by western blotting. EIF5A2 and its potential target metastasis-associated protein 1 (MTA1) expression were examined in 160 pairs of human gastric cancer and adjacent non-tumor specimens using immunohistochemistry (IHC) staining, and its correlation with clinicopathological features and survival was investigated. Knockdown of EIF5A2 or MTA1 caused an apparent suppression of HGC27 cell proliferation, migration and invasion. After knockdown of EIF5A2 in HGC27 cells, E-cadherin levels were upregulated and vimentin, cyclin D1, cyclin D3, C-MYC and MTA1 levels were downregulated. Upregulation of EIF5A2 in MKN45 cells resulted in the converse. IHC results showed a positive correlation between EIF5A2 and MTA1 expression in gastric cancers (P<0.001). Both EIF5A2 and MTA1 overexpression were correlated with pT stage (P=0.018 and P=0.042), pN stage (P=0.037 and P=0.020) and lymphovascular invasion (P=0.016 and P=0.044). EIF5A2 or MTA1 overexpression was significantly associated with poor overall survival and disease-free survival (All P<0.05). Multivariate analyses identified EIF5A2 as an independent predictor for both overall survival (P=0.012) and disease-free survival (P=0.008) in gastric cancer patients. Our findings indicate that EIF5A2 upregulation plays an important oncogenic role in gastric cancer. EIF5A2 may represent a new predictor for poor survival and is a potential therapeutic target for gastric cancer.

Long noncoding RNA CCAT1 promotes hepatocellular carcinoma progression by functioning as let-7 sponge

BACKGROUND

Long noncoding RNAs (lncRNAs) have been identified as having functional roles in cancer biology and are deregulated in many cancers. The present study aimed to determine the expression, roles and functional mechanisms of a long noncoding RNA CCAT1 in the progression of hepatocellular carcinoma (HCC).

METHODS

CCAT1 expression levels in 66 pairs of HCC tissues and pair-matched noncancerous hepatic tissues were tested by real-time PCR. The effects of CCAT1 on HCC cells proliferation and migration were assessed using in vitro cell proliferation and migration assays. A computational screen of microRNAs (miRNAs) target sites in CCAT1 was conducted to search for specific miRNAs binding to CCAT1. The specific binding between CCAT1 and miRNAs was confirmed by RNA immunoprecipitation assay combined with luciferase reporter assay.

RESULTS

CCAT1 levels are markedly increased in HCC tissues compared with pair-matched noncancerous hepatic tissues. Up-regulation of CCAT1 is correlated with tumor size, microvascular invasion, AFP and poor prognosis. CCAT1 promotes the proliferation and migration of HCC cells. CCAT1 functions as a molecular sponge for let-7, antagonizes its functions, and leads to the de-repression of its endogenous targets HMGA2 and c-Myc. The effect of CCAT1 on HCC cell proliferation and migration is dependent upon its competitively binding to let-7.

CONCLUSIONS

These data suggest that CCAT1 plays a pivotal role in HCC progression via functioning as let-7 sponge, and implicate the potential application of CCAT1 for the prognosis and treatment of HCC.

Long noncoding RNAs as a novel component of the Myc transcriptional network

Myc is a well-known transcription factor with important roles in cell cycle, apoptosis, and cellular transformation. Long noncoding RNAs (lncRNAs) have recently emerged as an important class of regulatory RNAs. Here, we show that lncRNAs are a main component of the Myc-regulated transcriptional program using the P493-6 tetracycline-repressible myc model. We demonstrate that both Myc-induced mRNAs and lncRNAs are significantly enriched for Myc binding sites. In contrast to Myc-repressed mRNAs, Myc-repressed lncRNAs are significantly enriched for Myc binding sites. Subcellular localization analysis revealed that compared to mRNAs, lncRNAs more often have a specific subcellular localization with a markedly higher percentage of nuclear enrichment within the Myc-repressed lncRNA set. Parallel analysis of differentially expressed lncRNAs and mRNAs identified 105 juxtaposed lncRNA-mRNA pairs, indicative for regulation in cis. To support the potential relevance of the Myc-regulated lncRNAs in cellular transformation, we analyzed their expression in primary Myc-high and Myc-low B-cell lymphomas. In total, 54% of the lncRNAs differentially expressed between the lymphoma subsets were identified as Myc-regulated in P493-6 cells. This study is the first to show that lncRNAs are an important factor within the Myc-regulated transcriptional program and indicates a marked difference between Myc-repressed lncRNAs and mRNAs.

Non-coding RNAs in gastric cancer

Non-coding RNAs (ncRNAs) have recently become increasingly important in the study of cellular metabolism and regulation such as development, proliferation, differentiation and apoptosis. However, the functions of most ncRNAs have remained largely unknown. Recently, studies have begun to characterize the aberrant regulation of ncRNAs in gastric cancer (GC) cells and tissues. These ncRNAs have a close relationship with drug resistance, and with the occurrence, development, invasion and metastasis of tumors, so they could possibly become new therapeutic targets and treatment tools for GC in the future. The present review summarized current advances in our knowledge of the roles of ncRNAs in GC.

Long noncoding RNA aberrant expression profiles after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy of AGC ascertained by microarray analysis

Long noncoding RNAs (lncRNAs) have been shown to be involved in the development and progression of advanced gastric cancer (AGC). However, the roles of lncRNAs in advanced gastric cancer during the process of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are not well understood. A high-throughput microarray analysis was performed to compare the expression profiles of lncRNAs and messenger RNAs (mRNAs) in AGC serum samples during the process of CRS + HIPEC. Several potentially AGC-associated lncRNAs were verified by real-time quantitative reverse transcription polymerase chain reaction (PCR) analysis. Using abundant and varied probes, we were able to assess 33,045 lncRNAs and 30,215 mRNAs in our microarray. We found that 566 lncRNAs were differentially expressed (2-fold change) in AGC serum samples, indicating the significantly up- or downregulated lncRNAs play important roles in AGC during the process of CRS + HIPEC. Quantitative PCR results further verified that eight lncRNAs were aberrantly expressed in AGC serum samples after CRS + HIEC compared with matched serum sample before CRS + HIPEC. Among them, BC031243 and RP11-356I2.2 were the most aberrantly expressed lncRNAs, as estimated by quantitative PCR in six pairs of AGC serum samples. Our study demonstrated the expression patterns of lncRNAs in AGC serums before and after CRS + HIPEC by microarray. These results revealed that lncRNAs were differentially expressed during the process of CRS + HIPEC, suggesting that they might play key roles in tumor development.