Long noncoding RNA BC032469, a novel competing endogenous RNA, upregulates hTERT expression by sponging miR-1207-5p and promotes proliferation in gastric cancer

Integrative Analysis of Dysregulated lncRNA-Associated ceRNA Network Reveals Functional lncRNAs in Gastric Cancer

Mounting evidence suggests that long noncoding RNAs (lncRNAs) play important roles in the regulation of gene expression by acting as competing endogenous RNA (ceRNA). However, the regulatory mechanisms of lncRNA as ceRNA in gastric cancer (GC) are not fully understood. Here, we first constructed a dysregulated lncRNA-associated ceRNA network by integrating analysis of gene expression profiles of lncRNAs, microRNAs (miRNAs), and messenger RNAs (mRNAs). Then, we determined three lncRNAs (RP5-1120P11, DLEU2, and DDX11-AS1) as hub lncRNAs, in which associated ceRNA subnetworks were involved in cell cycle-related processes and cancer-related pathways. Furthermore, we confirmed that the two lncRNAs (DLEU2 and DDX11-AS1) were significantly upregulated in GC tissues, promote GC cell proliferation, and negatively regulate miRNA expression, respectively. The hub lncRNAs (DLEU2 and DDX11-AS1) could have oncogenic functions, and act as potential ceRNAs to sponge miRNA. Our findings not only provide novel insights on ceRNA regulation in GC, but can also provide opportunities for the functional characterization of lncRNAs in future studies.

STARD13-correlated ceRNA network-directed inhibition on YAP/TAZ activity suppresses stemness of breast cancer via co-regulating Hippo and Rho-GTPase/F-actin signaling

BACKGROUND

Targeting cancer stem cells is critical for suppressing cancer progression and recurrence. Finding novel markers or related pathways could help eradicate or diagnose cancer in clinic.

METHODS

By constructing STARD13-correlated ceRNA 3'UTR stable overexpression or knockdown breast cancer cells, we aimed to explore the effects of STARD13-correlated ceRNA network on breast cancer stemness in vitro and in vivo. Further RNA-sequencing was used to analyze transcriptome change in combination with functional studies on candidate signaling. Clinical samples obtained from The Cancer Genome Atlas data were used to validate the correlation between STARD13 and related pathways. Finally, in vitro and in vivo experiments were used to examine the effects of STARD13-correlated ceRNA network on chemotherapy sensitivity/resistance.

RESULTS

Here, we revealed that this ceRNA network inhibited stemness of breast cancer. Mechanistically, we found that activation of STARD13-correlated ceRNA network was negatively correlated with YAP/TAZ activity in breast cancer. Specifically, this ceRNA network attenuated YAP/TAZ nuclear accumulation and transcriptional activity via collectively modulating Hippo and Rho-GTPase/F-actin signaling. Finally, we demonstrated that YAP/TAZ transcriptional activity regulated by this ceRNA network was involved in chemoresistance.

CONCLUSIONS

Our results uncover a novel mechanism of YAP/TAZ activation in breast cancer and propose the possibility to drive STARD13-correlated ceRNA network to inhibit breast cancer stem cell traits.

LncRNA MT1JP functions as a ceRNA in regulating FBXW7 through competitively binding to miR-92a-3p in gastric cancer

Background

Emerging evidence has shown that dysregulation function of long non-coding RNAs (lncRNAs) implicated in gastric cancer (GC). However, the role of the differentially expressed lncRNAs in GC has not fully explained.

Methods

LncRNA expression profiles were determined by lncRNA microarray in five pairs of normal and GC tissues, further validated in another 75 paired tissues by quantitative real-time PCR (qRT-PCR). Overexpression of lncRNA MT1JP was conducted to assess the effect of MT1JP in vitro and in vivo. The biological functions were demonstrated by luciferase reporter assay, western blotting and rescue experiments.

Results

LncRNA MT1JP was significantly lower in GC tissues than adjacent normal tissues, and higher MT1JP was remarkably related to lymph node metastasis and advance stage. Besides, GC patients with higher MT1JP expression had a well survival. Functionally, overexpression of lncRNA MT1JP inhibited cell proliferation, migration, invasion and promoted cell apoptosis in vitro, and inhibited tumor growth and metastasis in vivo. Functional analysis showed that lncRNA MT1JP regulated FBXW7 expression by competitively binding to miR-92a-3p. MiR-92a-3p and down-regulated FBXW7 reversed cell phenotypes caused by lncRNA MT1JP by rescue analysis.

Conclusion

MT1JP, a down-regulated lncRNA in GC, was associated with malignant tumor phenotypes and survival of GC. MT1JP regulated the progression of GC by functioning as a competing endogenous RNA (ceRNA) to competitively bind to miR-92a-3p and regulate FBXW7 expression. Our study provided new insight into the post-transcriptional regulation mechanism of lncRNA MT1JP, and suggested that MT1JP may act as a potential therapeutic target and prognosis biomarker for GC.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0829-6) contains supplementary material, which is available to authorized users.

LINC01410-miR-532-NCF2-NF-kB feedback loop promotes gastric cancer angiogenesis and metastasis

Dysregulation of non-coding RNAs, including miRNAs and lncRNAs has been reported to play vital roles in gastric cancer (GC) carcinogenesis, but the mechanism involved is largely unknown. Using the cancer genome atlas (TCGA) data set and bioinformatics analyses, we identified miR-532-5p as a potential tumor suppressor in GC, and found that lncRNA LINC01410 might be a negative regulator of miR-532-5p. We then conducted a series of in vivo and in vitro assays to explore the effect of LINC01410 on miR-532-5p-mediated GC malignancy and the underlying mechanism involved. MiR-532-5p overexpression inhibited GC metastasis and angiogenesis in vitro and in vivo, whereas miR-532-5p silencing had the opposite effect. Further study showed that miR-532-5p attenuated NF-κB signaling by directly inhibiting NCF2 expression, while miR-532-5p silencing in GC enhanced NF-κB activity. Furthermore, we demonstrated miR-532-5p down-regulation was caused by aberrantly high expression of LINC01410 in GC. Mechanistically, overexpression of LINC01410 promoted GC angiogenesis and metastasis by binding to and suppressing miR-532-5p, which resulted in up-regulation of NCF2 and sustained NF-κB pathway activation. Interestingly, NCF2 could in turn increase the promoter activity and expression of LINC01410 via NF-κB, thus forming a positive feedback loop that drives the malignant behavior of GC. Finally, high expression of LINC01410, along with low expression of miR-532-5p, was associated with poor survival outcome in GC patients. Our studies uncover a mechanism for constitutive LINC1410-miR-532-5p-NCF2-NF-κB feedback loop activation in GC, and consequently, as a potential therapeutic target in GC treatment.

Long noncoding RNA ZFAS1 promotes gastric cancer cells proliferation by epigenetically repressing KLF2 and NKD2 expression

Recently, long noncoding RNAs have been emerged as critical regulators of human disease and prognostic markers in several cancers, including gastric cancer. In this study, we globally assessed the transcriptomic differences of lncRNAs in gastric cancer using publicly available microarray data from Gene Expression Omnibus (GEO) and identified an oncogenetic lncRNA ZFAS1, which may promote gastric tumorigenesis. ZFAS1 has been found to be upregulated and function as oncogene in colorectal cancer and hepatocellular carcinoma, but its expression pattern, biological function and underlying mechanism in gastric cancer is still undetermined. Here, we reported that ZFAS1 expression is also overexpressed in gastric cancer, and its increased level is associated with poor prognosis and shorter survival. Knockdown of ZFAS1 impaired gastric cancer cells proliferation and induced apoptosis in vitro, and inhibited tumorigenicity of gastric cancer cells in vivo. Mechanistically, RNA immunoprecipitation and RNA pull-down experiment showed that ZFAS1 could simultaneously interact with EZH2 and LSD1/CoREST to repress underlying targets KLF2 and NKD2 transcription. In addition, rescue experiments determined that ZFAS1 oncogenic function is partly dependent on repressing KLF2 and NKD2. Taken together, our findings illuminate how ZFAS1 over-expression confers an oncogenic function in gastric cancer.

MicroRNA Regulation of Telomerase Reverse Transcriptase (TERT): Micro Machines Pull Strings of Papier-Mâché Puppets

Substantial fraction of high-quality information is continuously being added into the existing pool of knowledge related to the biology of telomeres. Based on the insights gleaned from decades of research, it is clear that chromosomal stability needs a highly controlled and dynamic balance of DNA gain and loss in each terminal tract of telomeric repeats. Telomeres are formed by tandem repeats of TTAGGG sequences, which are gradually lost with each round of division of the cells. Targeted inhibition of telomerase to effectively induce apoptosis in cancer cells has attracted tremendous attention and overwhelmingly increasingly list of telomerase inhibitors truthfully advocates pharmacological significance of telomerase. Telomerase reverse transcriptase (TERT) is a multi-talented and catalytically active component of the telomerase-associated protein machinery. Different proteins of telomerase-associated machinery work in a synchronized and orchestrated manner to ensure proper maintenance of telomeric length of chromosomes. Rapidly emerging scientific findings about regulation of TERT by microRNAs has revolutionized our understanding related to the biology of telomeres and telomerase. In this review, we have comprehensively discussed how different miRNAs regulate TERT in different cancers. Use of miRNA-based therapeutics against TERT in different cancers needs detailed research in preclinical models for effective translation of laboratory findings to clinically effective therapeutics.

Tag SNPs of long non-coding RNA TINCR affect the genetic susceptibility to gastric cancer in a Chinese population

Tissue differentiation-inducing non-protein coding RNA (TINCR) is required for normal epidermal differentiation. TINCR is also strongly overexpressed in human gastric cancer (GC) and contributes to carcinogenesis and tumor progression. However, the association between TINCR polymorphisms and the risk of any diseases, such as GC, remains unknown. In the present study, the tag single nucleotide polymorphisms rs8113645, rs2288947, rs8105637, and rs12610531 were analyzed in 602 patients with GC and 602 age- and sex-matched controls. Polymorphisms were genotyped using TaqMan technology. Carriers of variant rs8113645 and rs2288947 alleles indicated reduced risks of GC (p = 0.003 and 0.037, respectively). A allele genotypes of rs8113645 and G allele genotypes of rs2288947 (rs8113645 GA and AA; rs2288947 AG and GG) were also significantly associated with decreased GC risk (p < 0.05). Stratification analysis displayed that the correlations between GC risk and variant genotypes of both rs8113645 and rs2288947were more evident in younger individuals, men, nonsmokers, and individuals from rural areas. We also demonstrated that rs8113645 GA+AA genotype carriers had lower TINCR mRNA expression levels compared with common genotype in both normal and GC tissues (p < 0.05). These results suggest that long non-coding RNA TINCR polymorphisms may be implicated in GC development.

LncRNA H19 confers chemoresistance in ERα-positive breast cancer through epigenetic silencing of the pro-apoptotic gene BIK

Breast cancer is a common malignancy in women. Acquisition of drug resistance is one of the main obstacles encountered in breast cancer therapy. Long non-coding RNA (lncRNA) has been demonstrated to play vital roles in both development and tumorigenesis. However, the relationship between lncRNAs and the development of chemoresistance is not well established. In the present study, the high expression of lncRNA H19 was identified as a powerful factor associated with paclitaxel (PTX) resistance in ERα-positive breast cancer cells, but not in ERα-negative breast cancer cells. LncRNA H19 attenuated cell apoptosis in response to PTX treatment by inhibiting transcription of pro-apoptotic genes BIK and NOXA. H19 was further confirmed to suppress the promoter activity of BIK by recruiting EZH2 and by trimethylating the histone H3 at lysine 27. Interestingly, our data showed that lncRNA H19 was one of the downstream target molecules of ERα. Altered ERα expression may therefore change H19 levels to modulate the apoptosis response to chemotherapy in breast cancer cells. Our data suggest that the ERα-H19-BIK signaling axis plays an important role in promoting chemoresistance.

Long noncoding RNA GAS5 promotes bladder cancer cells apoptosis through inhibiting EZH2 transcription

Aberrant expression of long noncoding RNA GAS5 in bladder cancer (BC) cells was identified in recent studies. However, the regulatory functions and underlying molecular mechanisms of GAS5 in BC development remain unclear. Here, we confirmed that there was a negative correlation between GAS5 level and bladder tumor clinical stage. Functionally, overexpression of GAS5 reduced cell viability and induced cell apoptosis in T24 and EJ bladder cancer cells. Mechanistically, GAS5 effectively repressed EZH2 transcription by directly interacting with E2F4 and recruiting E2F4 to EZH2 promoter. We previously reported that miR-101 induced the apoptosis of BC cells by inhibiting the expression of EZH2. Interestingly, the present study showed that downregulation of EZH2 by GAS5 resulted in overexpression of miR-101 in T24 and EJ cells. Furthermore, the level of GAS5 was increased under the treatment of Gambogic acid (GA), a promising natural anti-cancer compound, whereas knockdown of GAS5 suppressed the inhibitory effect of GA on cell viability and abolished GA-induced apoptosis in T24 and EJ cells. Taken together, our findings demonstrated a tumor-suppressor role of GAS5 by inhibiting EZH2 on transcriptional level, and additionally provided a novel therapeutic strategy for treating human bladder cancer.

LncRNA DANCR functions as a competing endogenous RNA to regulate RAB1A expression by sponging miR-634 in glioma

Long noncoding RNA (lncRNA) differentiation antagonizing nonprotein coding RNA (DANCR) plays important regulatory roles in many solid tumors. However, the effect of DANCR in glioma progression and underlying molecular mechanisms were not entirely explored. In the present study, we determined the expression of DANCR in glioma tissues and cell lines using qRT-PCR and further defined the biological functions. Furthermore, we used luciferase reporter assay, Western blot, and RNA immunoprecipitation (RIP) to explore the underlying mechanism. Our results showed that DANCR was significantly up-regulated in glioma tissues and cell lines (U251, U118, LN229, and U87MG). High DANCR expression was correlated with advanced tumor grade. Inhibition of DANCR suppressed the glioma cells proliferation and induced cells arrested in the G0/G1 phase. In addition, we verified that DANCR could directly interact with miR-634 in glioma cells and this interaction resulted in the inhibition of downstream of RAB1A expression. The present study demonstrated that DANCR/miR-634/RAB1A axis plays crucial roles in the progression of glioma, and DANCR might potentially serve as a therapeutic target for the treatment of glioma patients.

Long noncoding RNA RP11-838N2.4 enhances the cytotoxic effects of temozolomide by inhibiting the functions of miR-10a in glioblastoma cell lines

Resistance to temolozomide (TMZ), the standard chemotherapy agent for treating glioblastomas (GBM), is a major clinical problem for patients with GBM. Recently, long noncoding RNAs (lncRNAs) have been implicated in chemotherapy resistance in various cancers. In this study, we found that the level of the lncRNA RP11-838N2.4 was lower in TMZ-resistant GBM cells (U87TR, U251TR) compared to the parental, non-resistant GBM cells (U87, U251). In GBM patients, the decreased level of lncRNA RP11-838N2.4 correlated with higher risk of GBM relapse, as well as shorter postoperative survival times. We further found that lncRNA RP11-838N2.4 could enhances the cytotoxic effects of temozolomide to GBM cells both in vivo and in vitro. Moreover, lncRNA RP11-838N2.4 acts as an endogenous sponge, suppressing the function of miR-10a through conserved sequences and increasing the expression of EphA8 that enhanced the rate of cell apoptosis, thereby intensified sensitivity of GBM cells to TMZ. Additionally, lncRNA RP11-838N2.4 inhibited the activity of transforming growth factor-β (TGF-β) independent of miR-10a. Finally, Characterization of lncRNA RP11-838N2.4 could contribute to strategies for enhancing the efficacy of TMZ.

Construction and Comprehensive Analysis for Dysregulated Long Non-Coding RNA (lncRNA)-Associated Competing Endogenous RNA (ceRNA) Network in Gastric Cancer

Long non-coding RNA (lncRNA) is a kind of non-coding RNA with transcripts more than 200 bp in length. LncRNA can interact with the miRNA as a competing endogenous RNA (ceRNA) to regulate the expression of target genes, which play a significant role in the initiation and progression of tumors. In this study, we explored the functional roles and regulatory mechanisms of lncRNAs as ceRNAs in gastric cancer, and their potential implications for prognosis. The lncRNAs, miRNAs, and mRNAs expression profiles of 375 gastric cancer tissues and 32 non-tumor gastric tissues were downloaded from The Cancer Genome Atlas (TCGA) database. Differential expression of RNAs was identified using the DESeq package. Survival analysis was estimated based on Kaplan-Meier curve analysis. KEGG pathway analysis was performed using KOBAS 3.0. The dysregulated lncRNA-associated ceRNA network was constructed in gastric cancer based on bioinformatics generated from miRcode and miRTarBase. A total of 237 differentially expressed lncRNAs and 198 miRNAs between gastric cancer and matched normal tissues were screened in our study with thresholds of |log2FC| >2 and adjusted P value <0.01. Eleven discriminatively expressed lncRNAs may be correlated with tumorigenesis of gastric cancer. Seven out of 11 dysregulated lncRNA were found to be significantly associated with overall survival in gastric cancer (P value <0.05). The newly identified ceRNA network includes 11 gastric cancer-specific lncRNAs, 9 miRNAs, and 41 mRNAs. Collectively, our study will contribute to improving the understanding of the lncRNA-associated ceRNA network regulatory mechanisms in the pathogenesis of gastric cancer and provide and identify novel lncRNAs as candidate prognostic biomarkers or potential therapeutic targets.

Post-transcriptional Regulation of Genes Related to Biological Behaviors of Gastric Cancer by Long Noncoding RNAs and MicroRNAs

Noncoding RNAs play critical roles in regulating protein-coding genes and comprise two major classes: long noncoding RNAs (lncRNAs) and microRNAs (miRNAs). LncRNAs regulate gene expression at transcriptional, post-transcriptional, and epigenetic levels via multiple action modes. LncRNAs can also function as endogenous competitive RNAs for miRNAs and indirectly regulate gene expression post-transcriptionally. By binding to the 3'-untranslated regions (3'-UTR) of target genes, miRNAs post-transcriptionally regulate gene expression. Herein, we conducted a review of post-transcriptional regulation by lncRNAs and miRNAs of genes associated with biological behaviors of gastric cancer.

Long noncoding RNA NORAD, a novel competing endogenous RNA, enhances the hypoxia-induced epithelial-mesenchymal transition to promote metastasis in pancreatic cancer

Background

Pancreatic cancer, one of the top two most fatal cancers, is characterized by a desmoplastic reaction that creates a dense microenvironment, promoting hypoxia and inducing the epithelial-to-mesenchymal transition (EMT) to facilitate invasion and metastasis. Recent evidence indicates that the long noncoding RNA NORAD may be a potential oncogenic gene and that this lncRNA is significantly upregulated during hypoxia. However, the overall biological role and clinical significance of NORAD remains largely unknown.

Methods

NORAD expression was measured in 33 paired cancerous and noncancerous tissue samples by real-time PCR. The effects of NORAD on pancreatic cancer cells were studied by overexpression and knockdown in vitro. Insights into the mechanism of competitive endogenous RNAs (ceRNAs) were gained from bioinformatics analyses and luciferase assays. In vivo, metastatic potential was identified using an orthotopic model of PDAC and quantified using bioluminescent signals. Alterations in RhoA expression and EMT levels were identified and verified by immunohistochemistry and Western blotting.

Results

NORAD is highly expressed in pancreatic cancer tissues and upregulated in hypoxic conditions. NORAD upregulation is correlated with shorter overall survival in pancreatic cancer patients. Furthermore, NORAD overexpression promoted the migration and invasion of pancreatic carcinoma cells, while NORAD depletion inhibited EMT and metastasis in vitro and in vivo. In particular, NORAD may function as a ceRNA to regulate the expression of the small GTP binding protein RhoA through competition for hsa-miR-125a-3p, thereby promoting EMT.

Conclusions

Elevated expression of NORAD in pancreatic cancer tissues is linked to poor prognosis and may confer a malignant phenotype upon tumor cells. NORAD may function as a ceRNA to regulate the expression of the small GTP binding protein RhoA through competition for hsa-miR-125a-3p. This finding may contribute to a better understanding of the role played by lncRNAs in hypoxia-induced EMT and provide a potential novel diagnostic and therapeutic target for pancreatic cancer.

Electronic supplementary material

The online version of this article (10.1186/s12943-017-0738-0) contains supplementary material, which is available to authorized users.

LncRNA RP11-436H11.5, functioning as a competitive endogenous RNA, upregulates BCL-W expression by sponging miR-335-5p and promotes proliferation and invasion in renal cell carcinoma

BACKGROUND

Accumulating evidence indicates that long non-coding RNAs (lncRNAs) play a crucial role in tumorigenesis. Here, we report a novel lncRNA, RP11-436H11.5, that regulates renal cell carcinoma (RCC) cell proliferation and invasion by sponging miR-335-5p.

METHODS

Expression of lncRNA RP11-436H11.5 was determined by a qRT-PCR assay in RCC tissues. RCC cell proliferation and invasion were measured by a cell proliferation assay and a transwell invasion assay. Expression of BCL-W was detected by a western blot assay. Interactions between lncRNA RP11-436H11.5 and miR-335-5p were measured by a luciferase reporter assay and a RNA-pull down assay. In vivo experiments were used to detect tumor formation.

RESULTS

In this study, the qRT-PCR results illustrated that lncRNA RP11-436H11.5 was more highly expressed in RCC tissues than in adjacent normal renal tissues. The results of survival analysis indicated that patients in the high lncRNA RP11-436H11.5 group presented significantly worse outcomes compared with those in the low lncRNA RP11-436H11.5 group. Downregulation of lncRNA RP11-436H11.5 suppressed RCC cell proliferation and invasion in vitro and in vivo. Luciferase reporter assay results demonstrated that lncRNA RP11-436H11.5 enhanced BCL-W expression by regulating miR-335-5p expression. LncRNA RP11-436H11.5 could function as a miR-335-5p decoy to derepress expression of BCL-W.

CONCLUSIONS

LncRNA RP11-436H11.5 could function as a competing endogenous RNA to promote RCC cell proliferation and invasion, which might serve as a therapeutic application to suppress RCC progression.

Prospective lncRNA-miRNA-mRNA regulatory network of long non-coding RNA LINC00968 in non-small cell lung cancer A549 cells: A miRNA microarray and bioinformatics investigation

Accumulating evidence suggests that the dysregulation of long non-coding RNAs (lncRNAs) serves vital roles in the incidence and progression of lung cancer. However, the molecular mechanisms of LINC00968, a recently identified lncRNA, remain unknown. The objective of present study was to investigate the role of a prospective lncRNA-miRNA‑mRNA network regulated by LINC00968 in non-small cell lung cancer cells. Following the transfection of lentiviruses carrying LINC00968 into A549 cells, the microRNA (miRNA) expression profile of the cells in response to the overexpression of LINC00968 was detected using an miRNA microarray. Five differentially expressed miRNAs (DEMs) with LINC00968 overexpression were obtained, including miR-9-3p, miR‑22-5p, miR-668-3p, miR‑3675-3p and miR-4536-3p. Five target prediction algorithms and three target validation algorithms were used to obtain 1,888 prospective target genes of the five DEMs. The result of Gene Ontology analysis suggested that these five DEMs were involved in complex cellular pathways, which included intracellular transport, organelle lumen and nucleotide binding. Furthermore, analysis of Kyoto Encyclopedia of Genes and Genomes pathways indicated that the five DEMs were important regulators in the adherens junction and focal adhesion. An lncRNA-miRNA-mRNA regulatory network and a protein-protein interaction network were then constructed. Eventually, a prospective lncRNA‑miRNA-mRNA regulatory network of LINC00968, three miRNAs (miR-9, miR-22 and miR-4536) and two genes (polo-like kinase 1 and exportin-1) was obtained following validation in the Cancer Genome Atlas database. These results may provide novel insights to support future research into lncRNA in lung cancer.

The lncRNA HOXA11-AS functions as a competing endogenous RNA to regulate PADI2 expression by sponging miR-125a-5p in liver metastasis of colorectal cancer

Several long non-coding RNAs (lncRNAs) play important roles in the regulation of liver metastasis in colorectal cancer (CRC) patients. We previously described the potential involvement of HOMEOBOX A11 (HOXA11) antisense RNA (HOXA11-AS), miR-125a-5p, and peptidyl arginine deiminase 2 (PADI2) in promoting liver metastasis in CRC patients. In the present study, we verified the significant upregulation of HOXA11-AS and PADI2, as well as the downregulation of miR-125a-5p, in CRC patients with liver metastasis. Overexpression and knockdown studies of HOXA11-AS or PADI2, as well as gain-/loss-of-function studies of miR-125a-5p, revealed a positive correlation between HOXA11-AS and PADI2 and a negative correlation with miR-125a-5p in the regulation of liver metastasis in CRC cell lines. Overall, we conclude that HOXA11-AS promotes liver metastasis in CRC by functioning as a miR-125a-5p sponge and describe a novel HOXA11-AS-miR-125a-5p-PADI2 regulatory network involved in CRC liver metastasis.

The long noncoding RNA TUG1 acts as a competing endogenous RNA to regulate the Hedgehog pathway by targeting miR-132 in hepatocellular carcinoma

Emerging evidence shows that the Hedgehog pathway and the long noncoding RNA TUG1 play pivotal roles in cell proliferation, migration, and invasion in tumors. However, the mechanism underlying the effect of TUG1 and the Hedgehog pathway in hepatoma remains undefined. In the present study, we showed that the expression of TUG1 was negatively correlated with that of microRNA (miR)-132, and depletion of TUG1 inhibited the activation of the Hedgehog pathway in vitro and in vivo. We showed that TUG1 functions as a competing endogenous (ceRNA) by competing with miR-132 for binding to the sonic hedgehog protein in HCC, thereby suppressing the activation of Hedgehog signaling and its tumorigenic effect. These data indicate that targeting the TUG1-miR132-Hedgehog network could be a new strategy for the treatment of HCC.

HBL1 Is a Human Long Noncoding RNA that Modulates Cardiomyocyte Development from Pluripotent Stem Cells by Counteracting MIR1

Cardiogenesis processes in human and animals have differential dynamics, suggesting the existence of species-specific regulators during heart development. However, it remains a challenge to discover the human-specific cardiac regulatory genes, given that most coding genes are conserved. Here, we report the identification of a human-specific long noncoding RNA, Heart Brake LncRNA 1 (HBL1), which regulates cardiomyocyte development from human induced pluripotent stem cells (hiPSCs). Overexpression of HBL1 repressed, whereas knockdown and knockout of HBL1 increased, cardiomyocyte differentiation from hiPSCs. HBL1 physically interacted with MIR1 in an AGO2 complex. Disruption of MIR1 binding sites in HBL1 showed an effect similar to that of HBL1 knockout. SOX2 bound to HBL1 promoter and activated its transcription. Knockdown of SOX2 in hiPSCs led to decreased HBL1 expression and increased cardiomyocyte differentiation efficiency. Thus, HBL1 plays a modulatory role in fine-tuning human-specific cardiomyocyte development by forming a regulatory network with SOX2 and MIR1.

The role of miRNA and lncRNA in gastric cancer

Gastric cancer is one of the most common cancers and has the highest mortality rate worldwide. It is worthwhile to explore the mechanism of gastric cancer progression. An increasing number of studies have found that non-coding RNAs including miRNA and lncRNA play important roles in gastric cancer progression. This review summarized the role of ectopic miRNA in gastric cancer proliferation, growth, migration, invasion and apoptosis. Meantime, aberrantly expressed miRNA also received a great deal of attention as potential biomarker for gastric cancer diagnosis and therapy. Over the last decade, lncRNA was considered to regulate gastric cancer progression at the transcript and post-transcript level. At the transcript level, lncRNA induced gastric cancer progression by changing chromatin modification and mRNA stabilization to regulate mRNA and miRNA expression. Furthermore, lncRNA regulated gastric cancer progression by completely combining with miRNA to produce ceRNA or promote protein stabilization at the post-transcript level. Greater attention of miRNA and lncRNA in gastric cancer can provide new insight of mechanism of cancer development and may be acted as a new anticancer target.

Long non-coding RNA UBE2CP3 promotes tumor metastasis by inducing epithelial-mesenchymal transition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly aggressive, solid malignancy that has a poor prognosis. Long non-coding RNAs (lncRNAs) have been found to be dysregulated in various cancers, including HCC. However, the molecular mechanism involving lncRNAs in HCC remains largely unknown. In this study, lncRNAs differentially expressed between HCC and corresponding non-cancerous tissue were identified by microarray analysis. A specific differentially expressed lncRNA UBE2CP3 (ubiquitin conjugating enzyme E2 C pseudogene 3) was identified. LncRNA UBE2CP3 was frequently up-regulated in HCC samples as assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) experiments. Clinical data showed that high levels of lncRNA UBE2CP3 were correlated with poor prognosis in HCC patients. Functional studies demonstrated that over-expression of lncRNA UBE2CP3 promoted cell invasion and migration in vitro and in vivo. Mechanistically, enhanced expression of lncRNA UBE2CP3 increased the expression of Snail1 and N-cadherin, but decreased the expression of E-cadherin, thus promoting the process of epithelial to mesenchymal transition (EMT) and finally inducing cell invasion and migration. Furthermore, serum levels of lncRNA UBE2CP3 were increased in HCC patients and decreased after surgery. Our results suggest that lncRNA UBE2CP3 promotes the metastasis of HCC and that serum lncRNA UBE2CP3 may be a new biomarker for the diagnosis of HCC.

Long non-coding RNA MALAT1 promotes proliferation and suppresses apoptosis of glioma cells through derepressing Rap1B by sponging miR-101

Long non-coding RNAs (lncRNAs) have been recently shown to be dysregulated and closely related to several cancers. Here, we aimed to elucidate the function and the possible molecular mechanisms of lncRNA Metastasis-associated lung Adenocarcinoma transcript-1 (MALAT1) in human glioma. Quantitative real-time PCR (qRT-PCR) was used to detect the expressions of MALAT1, miR-101 and Rap1B mRNA in U251 and U87 cells. The protein level of Rap1B was examined by western blot assays. Moreover, the proliferation and apoptosis of U251 and U87 cells were determined by CCK-8 assay and flow cytometry analysis, respectively. Additionally, the targets of miR-101 were identified by target prediction and luciferase reporter assays. The results demonstrated that MALAT1 and Rap1B were upregulated, while miR-101 expression was downregulated in glioma cell lines U251 and U87. MALAT1 and Rap1B knockdown could inhibit proliferation and induce apoptosis of glioma cells. Moreover, MALAT1 promoted the Rap1B expression by sponging miR-101 in U251 and U87 cells. Furthermore, miR-101 downregulation or Rap1B overexpression reversed the proliferation inhibitory and apoptosis induction of glioma cell lines caused by MALAT1 knockdown. Taken together, MALAT1 promotes proliferation and suppresses apoptosis of glioma cells through derepressing Rap1B by sponging miR-101. The present study elucidates a novel MALAT1-miR-101-Rap1B regulatory axis in glioma, contributing to a better understanding of the glioma pathogenesis and providing a promising therapeutic target for glioma patients.

PVT1-derived miR-1207-5p promotes breast cancer cell growth by targeting STAT6

Accumulating evidence indicates that ectopic expression of non‐coding RNAs are responsible for breast cancer progression. Increased non‐coding RNA PVT1, the host gene of microRNA‐1207‐5p (miR‐1207‐5p), has been associated with breast cancer proliferation. However, how PVT1 functions in breast cancer is still not clear. In this study, we show a PVT1‐derived microRNA, miR‐1207‐5p, that promotes the proliferation of breast cancer cells by directly regulating STAT6. We first confirm the positive correlated expression pattern between PVT1 and miR‐1207‐5p by observing consistent induced expression by estrogen, and overexpression in breast cancer cell lines and breast cancer patient specimens. Moreover, silence of PVT1 also decreased miR‐1207‐5p expression. Furthermore, increased miR‐1207‐5p expression promoted, while decreased miR‐1207‐5p expression suppressed, cell proliferation, colony formation, and cell cycle progression in breast cancer cell lines. Mechanistically, a novel target of miR‐1207‐5p,STAT6, was identified by a luciferase reporter assay. Overexpression of miR‐1207‐5p decreased the levels of STAT6, which activated CDKN1A and CDKN1B to regulate the cell cycle. We also confirmed the reverse correlation of miR‐1207‐5p and STAT6 expression levels in breast cancer samples. Therefore, our findings reveal that PVT1‐derived miR‐1207‐5p promotes the proliferation of breast cancer cells by targeting STAT6, which in turn controls CDKN1A and CDKN1B expression. These findings suggest miR‐1207‐5p might be a potential target for breast cancer therapy.

A meta-analysis: The diagnostic values of long non-coding RNA as a biomarker for gastric cancer

Long non-coding RNAs (lncRNAs) have been identified as novel biomarkers for the diagnosis, staging and prognosis for gastric cancer. However, various studies have reported a series of significances based on different diagnostic values. Therefore, the current study performed a systematic review and meta-analysis to evaluate the diagnostic accuracy of lncRNAs for gastric cancer, and to discuss lncRNA types and sources of heterogeneity. The Cochrane Central Register of Controlled Trials, MEDLINE, PubMed, EMBASE, the Chinese Biomedical Literature Database, the China Academic Journals Full-text Database and the Chinese Scientific Journals Database were systematically searched for potential studies. Studies were included if they were associated with lncRNAs, gastric cancer and reported diagnostic outcomes. Analysis of diagnostic values was used to summarize the overall test performance of lncRNAs. Ten studies were included in this meta-analysis. The ranges of the diagnostic value of lncRNAs for gastric cancer were as follows: Sensitivity was 0.45–0.83, and pooled sensitivity was 0.63; specificity was 0.60–0.93, and pooled specificity was 0.75; positive likelihood ratio was 1.80–6.92, and pooled positive likelihood ratio was 2.51; negative likelihood ratio was 0.23–0.67, and pooled negative likelihood ratio was 0.50; diagnostic odds ratio was 3.33–13.75, and pooled diagnostic odds ratio was 5.47. An overall area under the curve value of the summary receiver operating characteristic curve was 0.7550. LncRNAs did not have a high accuracy for identifying gastric cancer at present, but may be a useful screening tool for diagnosing gastric cancer due to their correlation with gastric cancer biological features. LncRNAs are potential biomarkers for gastric cancer if the screening strategy is altered, or they are combined with other biomarkers to diagnose gastric cancer.

Knockdown of Long Noncoding RNA TUG1 Inhibits the Proliferation and Cellular Invasion of Osteosarcoma Cells by Sponging miR-153

Long noncoding RNA (lncRNA) taurine-upregulated gene 1 (TUG1) has been confirmed to be involved in the progression of various cancers; however, its mechanism of action in osteosarcoma has not been well addressed. In our study, TUG1 was overexpressed and miR-153 was downregulated in osteosarcoma tissues and cell lines. A loss-of-function assay showed that TUG1 knockdown suppressed the viability, colony formation, and invasion of osteosarcoma cells in vitro. Moreover, TUG1 was confirmed to be an miR-153 sponge. Ectopic expression of TUG1 reversed the inhibitory effect of miR-153 on the proliferation and invasion of osteosarcoma cells. Further transplantation experiments proved the carcinogenesis of TUG1 in osteosarcoma in vivo. Collectively, our study elucidated that TUG1 contributes to the development of osteosarcoma by sponging miR-153. These findings may provide a novel lncRNA-targeted therapy for patients with osteosarcoma.

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

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

Knockdown of long non-coding RNA XIST increases blood-tumor barrier permeability and inhibits glioma angiogenesis by targeting miR-137

Antiangiogenic therapy plays a significant role in combined glioma treatment. However, poor permeability of the blood–tumor barrier (BTB) limits the transport of chemotherapeutic agents, including antiangiogenic drugs, into tumor tissues. Long non-coding RNAs (lncRNAs) have been implicated in various diseases, especially malignant tumors. The present study found that lncRNA X-inactive-specific transcript (XIST) was upregulated in endothelial cells that were obtained in a BTB model in vitro. XIST knockdown increased BTB permeability and inhibited glioma angiogenesis. The analysis of the mechanism of action revealed that the reduction of XIST inhibited the expression of the transcription factor forkhead box C1 (FOXC1) and zonula occludens 2 (ZO-2) by upregulating miR-137. FOXC1 decreased BTB permeability by increasing the promoter activity and expression of ZO-1 and occludin, and promoted glioma angiogenesis by increasing the promoter activity and expression of chemokine (C–X–C motif) receptor 7b (CXCR7). Overall, the present study demonstrates that XIST plays a pivotal role in BTB permeability and glioma angiogenesis, and the inhibition of XIST may be a potential target for the clinical management of glioma.

Long Noncoding RNA MEG3 Suppresses Glioma Cell Proliferation, Migration, and Invasion by Acting as a Competing Endogenous RNA of miR-19a

Glioma, with varying malignancy grades and histological subtypes, is the most common primary brain tumor in adults. Long noncoding RNAs (lncRNAs) are non-protein-coding transcripts and have been proven to play an important role in tumorigenesis. Our study aims to elucidate the combined effect of lncRNA maternally expressed gene 3 (MEG3) and microRNA-19a (miR-19a) in human glioma U87 and U251 cell lines. Real-time PCR revealed that MEG3 was downregulated and miR-19a was upregulated in malignant glioma tissues and cell lines. Bioinformatics analyses (TargetScan, miRanda, and starBase V2.0) showed that phosphatase and tensin homolog (PTEN) is a target of miR-19a with complementary binding sites in the 3'-UTR. As expected, luciferase results verified the putative target site and also revealed the complementary binding between miR-19a and MEG3. miR-19a represses the expression of PTEN and promotes glioma cell proliferation, migration, and invasion. However, MEG3 could directly bind to miR-19a and effectively act as a competing endogenous RNA (ceRNA) for miR-19a to suppress tumorigenesis. Our study is the first to demonstrate that lncRNA MEG3 suppresses glioma cell proliferation, migration, and invasion by acting as a ceRNA of miR-19a, which provides a novel insight about the pathogenesis of glioma.

Long noncoding AGAP2-AS1 is activated by SP1 and promotes cell proliferation and invasion in gastric cancer

BACKGROUND

Long noncoding RNAs (lncRNAs) have emerged as important regulators of tumorigenesis and cancer progression. Recently, the lncRNA AGAP2-AS1 was identified as an oncogenic lncRNA in human non-small cell lung cancer (NSCLC) and its elevated expression was linked to NSCLC development and progression. However, the expression pattern and molecular mechanism of AGAP2-AS1 in gastric cancer (GC) have not been characterized.

METHODS

Bioinformatic analysis was performed to determine AGAP2-AS1 expression levels in the GC and normal tissues using gene profiling data from the Gene Expression Omnibus. Quantitative real-time polymerase chain reaction was used to validate AGAP2-AS1 expression in the GC tissues/cell lines compared with that in the adjacent nontumorous tissues/normal epithelial cells. Loss- and gain-of-function approaches were performed to investigate the effect of AGAP2-AS1 on GC cell phenotypes. The effect of AGAP2-AS1 on cell proliferation was evaluated by MTT, colony formation, flow cytometry, and in vivo tumor formation assays. The effects of AGAP2-AS1 on cell migration and invasion were examined using Transwell assays. Chromatin immunoprecipitation, luciferase reporter assays, RNA pull-down, and RNA immunoprecipitation were used to investigate the factors involved in AGAP2-AS1 dysregulation and the mechanism of action of AGAP2-AS1 in the GC cells.

RESULTS

AGAP2-AS1 was highly expressed in the GC tissues and cell lines, and patients with higher AGAP2-AS1 expression had a poorer prognosis and shorter overall survival. Furthermore, knockdown of AGAP2-AS1 significantly inhibited GC cell proliferation, migration, and invasion in vitro and tumor growth in vivo. AGAP2-AS1 overexpression promoted cell growth and invasion. In addition, the transcription factor SP1 activated AGAP2-AS1 expression in the GC cells. AGAP2-AS1 functions as an oncogenic lncRNA by interacting with LSD1 and EZH2 and suppressing CDKN1A (P21) and E-cadherin transcription.

CONCLUSIONS

Taken together, these findings imply that AGAP2-AS1 upregulated by SP1 plays an important role in GC development and progression by suppressing P21 and E-cadherin, which suggests that AGAP2-AS1 is a potential diagnostic marker and therapeutic target for GC patients.

Long non-coding RNAs in anti-cancer drug resistance

Chemotherapy is one of the basic treatments for cancers; however, drug resistance is mainly responsible for the failure of clinical treatment. The mechanism of drug resistance is complicated because of interaction among various factors including drug efflux, DNA damage repair, apoptosis and targets mutation. Long non-coding RNAs (lncRNAs) have been a focus of research in the field of bioscience, and the latest studies have revealed that lncRNAs play essential roles in drug resistance in breast cancer, gastric cancer and lung cancer, et al. Dysregulation of multiple targets and pathways by lncRNAs results in the occurrence of chemoresistance. In this review, we will discuss the mechanisms underlying lncRNA-mediated resistance to chemotherapy and the therapeutic potential of lncRNAs in future cancer treatment.

Long non-coding RNA LINC00152 promotes gallbladder cancer metastasis and epithelial-mesenchymal transition by regulating HIF-1α via miR-138

Long non-coding RNA LINC00152 had been reported as an oncogene in gastric and hepatocellular cancer. In this study, we show that LINC00152 is overexpressed in gallbladder cancer (GBC) tissue samples and cell lines. The high LINC00152 levels correlated negatively with the overall survival time in GBC patients. Functionally, LINC00152 dramatically promoted cell migration, invasion and epithelial-mesenchymal transition (EMT) progression in vitro. In vivo, LINC00152 overexpression significantly promoted tumour peritoneal spreading and metastasis. Mechanistic analyses indicated that LINC00152 functions as a molecular sponge for miR-138, which directly suppresses the expression of hypoxia inducible factor-1α (HIF-1α). We revealed that miR-138 is a suppressor of GBC cell metastasis and EMT progression, and a similar phenomenon was observed in HIF-1α knockdown NOZ cells. Through binding to miR-138, LINC00152 has an oncogenic effect on GBC. Overall, our study suggested that the LINC00152/miR-138/HIF-1α pathway potentiates the progression of GBC, and LINC00152 may be a novel therapeutic target.

Long Noncoding RNA: Genome Organization and Mechanism of Action

For the last four decades, we have known that noncoding RNAs maintain critical housekeeping functions such as transcription, RNA processing, and translation. However, in the late 1990s and early 2000s, the advent of high-throughput sequencing technologies and computational tools to analyze these large sequencing datasets facilitated the discovery of thousands of small and long noncoding RNAs (lncRNAs) and their functional role in diverse biological functions. For example, lncRNAs have been shown to regulate dosage compensation, genomic imprinting, pluripotency, cell differentiation and development, immune response, etc. Here we review how lncRNAs bring about such copious functions by employing diverse mechanisms such as translational inhibition, mRNA degradation, RNA decoys, facilitating recruitment of chromatin modifiers, regulation of protein activity, regulating the availability of miRNAs by sponging mechanism, etc. In addition, we provide a detailed account of different mechanisms as well as general principles by which lncRNAs organize functionally different nuclear sub-compartments and their impact on nuclear architecture.

LncRNA HOTAIR promotes cisplatin resistance in gastric cancer by targeting miR-126 to activate the PI3K/AKT/MRP1 genes

Altered expression of long noncoding RNAs (lncRNAs) has shown to associate with human cancer development and progression and drug resistance. LncRNA HOX antisense intergenic RNA (HOTAIR) regulates chromatin state and highly expressed in various human cancers. This study analyzed HOTAIR expression in gastric cancer cells and tissues and then assessed the effects of HOTAIR on modulation of gastric cancer cell sensitivity to cisplatin and the underlying molecular events. The data showed that HOTAIR was significantly upregulated in cisplatin-resistant gastric cancer cells and tissues compared with control cells and noncancerous gastric tissues. Overexpression of HOTAIR enhanced gastric cancer cell proliferation, promoted cell cycle G1/S transition, but decreased tumor cell apoptosis. Furthermore, HOTAIR was shown to directly bind to and inhibit miR-126 expression and then to promote VEGFA and PIK3R2 expression and activate the PI3K/AKT/MRP1 pathway. In conclusion, the data demonstrated that high HOTAIR expression acted as a competitive endogenous RNA to promote cisplatin resistance in gastric cancer. Further study will evaluate HOTAIR expression as a biomarker to predict treatment response of cisplatin and explore inhibition of HOTAIR expression as a novel strategy for anti-cisplatin resistance in human gastric cancer.

Upregulated long non-coding RNA BC032469 enhances carcinogenesis and metastasis of esophageal squamous cell carcinoma through regulating hTERT expression

Currently, long non-coding RNAs (lncRNAs) have been shown to have critical regulatory roles in various cancers. However, its role in esophageal squamous cell carcinoma (ESCC) remains largely unknown. Here, we focused on lncRNA BC032469, one of the lncRNAs involved in the development of ESCC. The levels of a specific differentially expressed lncRNA (termed lncRNA-BC032469) were measured in 45 paired esophageal squamous cell carcinoma tissue samples by quantitative real-time RT-PCR and then subjected to correlation analysis with clinical parameters and prognosis. The functions of lncRNA-BC032469 were evaluated by silencing and overexpressing the lncRNA in vitro and in vivo. The expression level of BC032469 in esophageal squamous cell carcinoma tissues was higher than that in the corresponding non-cancerous tissues. High BC032469 levels were correlated with lymph node metastasis, TNM stage, and tumor size and lower overall survival. Knockdown of BC032469 in TE13 and Eca109 cells inhibited cell proliferation, migration, and invasion; induced cell cycle arrest in the G0/G1 phase; and promoted apoptosis. Western blot analysis revealed that BC032469 regulated the expression of human telomerase reverse transcriptase (hTERT), which is important for cell proliferation and metastasis. Moreover, the restored expression of hTERT protein in BC032469-knockdown cells attenuated the suppressive effects of BC032469 on ESCC cells. Collectively, these results indicated that lncRNA-BC032469 is an oncogenic lncRNA that promotes tumor progression and leads us to propose that lncRNAs may serve as key regulatory hubs in ESCC development.

The lncRNA SNHG5/miR-32 axis regulates gastric cancer cell proliferation and migration by targeting KLF4

Long noncoding RNAs (lncRNAs) are emerging as important regulators in cellular processes, including the development, proliferation, and migration of cancer cells. We have demonstrated in a prior study that small nucleolar RNA host gene 5 (SNHG5) is dysregulated in gastric cancer (GC). To further explore the underlying mechanisms of SNGH5 function in the development of GC, in this study, we screened the microRNAs interacting with SNHG5 and elucidated their roles in GC. We showed that SNHG5 contains a putative miR-32-binding site and that deletion of this site abolishes the responsiveness to miR-32. Suppression of SNHG5 expression by miR-32 was found to be Argonaute (Ago)2-dependent. Immunoprecipitation showed that SNHG5 could be pulled down from the Ago-2 complex with miR-32. Furthermore, it was reported that Kruppel-like factor 4 (KLF4) is a target gene of miR-32. In agreement with SNHG5 being a decoy for miR-32, we showed that KLF4 suppression by miR-32 could be partially rescued by SNHG5 overexpression, whereas miR-32 mimic rescued SNHG5 overexpression-mediated suppression of GC cell migration. In addition, we identified a negative correlation between the expression of SNHG5 and miR-32 in GC tissues. Furthermore, KLF4 expression was significantly downregulated in GC specimens, and a negative correlation between miR-32 and KLF4 expression and a positive correlation between KLF4 and SNHG5 expression levels were detected. Overall, this study demonstrated, for the first time, that the SNHG5/miR-32/KLF4 axis functions as an important player in GC cell migration and potentially contributes to the improvement of GC diagnosis and therapy.-Zhao, L., Han, T., Li, Y., Sun, J., Zhang, S., Liu, Y., Shan, B., Zheng D., Shi, J. The lncRNA SNHG5/miR-32 axis regulates gastric cancer cell proliferation and migration by targeting KLF4.

Roles of long noncoding RNAs in gastric cancer and their clinical applications

PURPOSE

Gastric cancer ranks as the most common cancer in the world. However, the progresses of its diagnosis and treatment are still not satisfactory. The purpose of this study is to summarize the roles of lncRNAs associated with gastric cancer.

METHODS

We searched lncRNAs associated with gastric cancer in PubMed.

RESULTS

Long noncoding RNAs (lncRNAs), transcripts larger than 200 nucleotides, regulate gene expression at various levels. They are playing important roles in the occurrence and development of gastric cancer. They are involved in signaling pathways, crosstalk with microRNAs, and affecting metastasis by regulating epithelial-to-mesenchymal transition. By acting as oncogenes or tumor suppressors, lncRNAs contribute to gastric cancer occurrence and development. Several lncRNAs including HOTAIR, HULC, LINC00152, MALAT2, H19, GHET1, and GACAT3 have been demonstrated having oncogene activities, while other lncRNAs including LEIGC, GAS5, and FER1L4 have been thought as tumor suppressors.

CONCLUSIONS

Several lncRNAs from tissue, blood, and gastric juice have shown potential values in gastric cancer diagnosis or prognosis evaluation.

Long non-coding RNA MALAT1 acts as a competing endogenous RNA to promote malignant melanoma growth and metastasis by sponging miR-22

Long non-coding RNAs (lncRNAs) are involved in tumorigenesis. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), an lncRNAs, is associated with the growth and metastasis of many human tumors, but its biological roles in malignant melanoma remain unclear. In this study, the aberrant up-regulation of MALAT1 was detected in melanoma. We determined that MALAT1 promotes melanoma cells proliferation, invasion and migration by sponging miR-22. MiR-22 was decreased and acted as a tumor suppressor in melanoma, and MMP14 and Snail were the functional targets of miR-22. Furthermore, MALAT1 could modulate MMP14 and Snail by operating as a competing endogenous RNA (ceRNA) for miR-22. The effects of MALAT1 in malignant melanoma is verified using a xenograft model. This finding elucidates a new mechanism for MALAT1 in melanoma development and provides a potential target for melanoma therapeutic intervention.

Novel long non-coding RNA GACAT3 promotes gastric cancer cell proliferation through the IL-6/STAT3 signaling pathway

Long non-coding RNAs (lncRNAs) play an important role in cancer occurrence and development. We previously demonstrated that lncRNA gastric cancer-associated transcript 3 (GACAT3) was positively correlated with TNM stages, tumor size, and distant metastasis of patients with gastric cancer. However, the role of GACAT3 in gastric cancer remains unclear. In this study, to investigate its function, we synthesized small interference RNAs (siRNAs) against GACTA3 and developed a GACAT3 overexpression vector (pcDNA3-GACAT3), respectively. The siRNA-mediated knockdown of GACAT3 significantly decreased cell proliferation of the gastric cancer HGC-27 cells, in which GACAT3 is overexpressed. Furthermore, GACAT3 overexpression in gastric cancer SGC-7901 cells promoted cell growth. Moreover, GACAT3 expression in HGC-27 cells was greatly upregulated by IL-6 treatment in a concentration-dependent manner. In contrast, siRNA-mediated knockdown of STAT3 decreased GACAT3 expression even in the presence of IL-6. These results demonstrated that as a downstream target of the IL6/STAT3 signaling, lncRNA GACAT3 promotes gastric cancer cell growth suggesting that GACAT3 is an inflammatory response gene and may be served as a valuable potential target for the treatment of gastric cancer.

Noncoding RNAs in gastric cancer: Research progress and prospects

Noncoding RNAs (ncRNAs) have attracted much attention in cancer research field. They are involved in cellular development, proliferation, differentiation and apoptosis. The dysregulation of ncRNAs has been reported in tumor initiation, progression, invasion and metastasis in various cancers, including gastric cancer (GC). In the past few years, an accumulating body of evidence has deepened our understanding of ncRNAs, and several emerging ncRNAs have been identified, such as PIWI-interacting RNAs (piRNAs) and circular RNAs (circRNAs). The competing endogenous RNA (ceRNA) networks include mRNAs, microRNAs, long ncRNAs (lncRNAs) and circRNAs, which play critical roles in the tumorigenesis of GC. This review summarizes the recent hotspots of ncRNAs involved in GC pathobiology and their potential applications in GC. Finally, we briefly discuss the advances in the ceRNA network in GC.

The lncRNA MALAT1 functions as a competing endogenous RNA to regulate MCL-1 expression by sponging miR-363-3p in gallbladder cancer

Gallbladder carcinoma (GBC) is an aggressive neoplasm, and the treatment options for advanced GBC are limited. Recently, long non‐coding RNAs (lncRNAs) have emerged as new gene regulators and prognostic markers in several cancers. In this study, we found that metastasis‐associated lung adenocarcinoma transcript 1 (MALAT1) expression was up‐regulated in GBC tissues (P < 0.05). Luciferase reporter assays and RNA pull down assays showed that MALAT1 is a target of miR‐363‐3p. Real‐time quantitative PCR and Western blot analysis indicated that MALAT1 regulated Myeloid cell leukaemia‐1 (MCL‐1) expression as a competing endogenous RNA (ceRNA) for miR‐363‐3p in GBC cells. Furthermore, MALAT1 silencing decreased GBC cell proliferation and the S phase cell population and induced apoptosis in vitro. In vivo, tumour volumes were significantly decreased in the MALAT1 silencing group compared with those in the control group. These data demonstrated that the MALAT1/miR‐363‐3p/MCL‐1 regulatory pathway controls the progression of GBC. Inhibition of MALAT1 expression may be to a novel therapeutic strategy for gallbladder cancer.

Regulation of the Telomerase Reverse Transcriptase Subunit through Epigenetic Mechanisms

Chromosome-shortening is characteristic of normal cells, and is known as the end replication problem. Telomerase is the enzyme responsible for extending the ends of the chromosomes in de novo synthesis, and occurs in germ cells as well as most malignant cancers. There are three subunits of telomerase: human telomerase RNA (hTERC), human telomerase associated protein (hTEP1), or dyskerin, and human telomerase reverse transcriptase (hTERT). hTERC and hTEP1 are constitutively expressed, so the enzymatic activity of telomerase is dependent on the transcription of hTERT. DNA methylation, histone methylation, and histone acetylation are basic epigenetic regulations involved in the expression of hTERT. Non-coding RNA can also serve as a form of epigenetic control of hTERT. This epigenetic-based regulation of hTERT is important in providing a mechanism for reversibility of hTERT control in various biological states. These include embryonic down-regulation of hTERT contributing to aging and the upregulation of hTERT playing a critical role in over 90% of cancers. Normal human somatic cells have a non-methylated/hypomethylated CpG island within the hTERT promoter region, while telomerase-positive cells paradoxically have at least a partially methylated promoter region that is opposite to the normal roles of DNA methylation. Histone acetylation of H3K9 within the promoter region is associated with an open chromatin state such that transcription machinery has the space to form. Histone methylation of hTERT has varied control of the gene, however. Mono- and dimethylation of H3K9 within the promoter region indicate silent euchromatin, while a trimethylated H3K9 enhances gene transcription. Non-coding RNAs can target epigenetic-modifying enzymes, as well as transcription factors involved in the control of hTERT. An epigenetics diet that can affect the epigenome of cancer cells is a recent fascination that has received much attention. By combining portions of this diet with epigenome-altering treatments, it is possible to selectively regulate the epigenetic control of hTERT and its expression.

Role of competing endogenous RNAs in development of gastric cancer

Gastric cancer is one of the most common digestive system tumors and the second cause of malignancy related death, and it is caused by multiple factors such as genetic susceptibility, environment and living habits. It is reported that members of competitive endogenous RNAs, including microRNAs and long non-coding RNAs, play an important role in gastric cancer development. This article reviews the role of competing endogenous RNAs in the development of gastric cancer.

SPRY4 Intronic Transcript 1 Promotes Epithelial-Mesenchymal Transition Through Association with Snail1 in Osteosarcoma

Osteosarcoma is an aggressive tumor and the most common malignancy of the skeleton. Due to pulmonary metastasis, the 5-year survival rate is still unsatisfactory. It has been reported that SPRY4 intronic transcript 1 (SPRY4-IT1) promotes cell growth, invasion, and inhibits apoptosis in several cancers. However, the role of SPRY4-IT1 in osteosarcoma remains unclear. In the present study, we investigated the role of SPRY4-IT1 in osteosarcoma cells. Loss- and gain-of-function assays demonstrated that SPRY4-IT1 promoted cell proliferation, migration, and invasion in osteosarcoma. Moreover, SPRY4-IT1 induced epithelial-mesenchymal transition phenotype in osteosarcoma cells. Subsequent investigations revealed that SPRY4-IT1 promoted migration and invasion through association with Snail1 and regulating its stability. Based on these findings, the SPRY4-IT1/Snail1/E-cadherin pathway may play a crucial role in promoting osteosarcoma metastasis. Thus, SPRY4-IT1 may be a potential target for new therapies of osteosarcoma.