Low expression of lncRNA-HMlincRNA717 in human gastric cancer and its clinical significances

Evaluation of expression level of BANCR, MALAT1 and FER1L4 and their target genes in coumarin-treated AGS cell line

Because long non-coding RNAs (lncRNAs) can affect several interconnected processes, its value as a predictive marker for gastric cancer has been demonstrated. Coumarin - a natural compound known to contain some beneficial antitumor qualities - was tested for its effects on AGS gastric cancer cells. In this study, we investigated the expression level of selected cellular lncRNAs (BANCR, MALAT1 and FER1L4) and their target genes (PTEN, p-PI3K and p-AKT) in coumarin-treated AGS cell line. The expressions of the three lncRNAs: BANCR, MALAT1 and FER1L4, as well as their specified targets, PTEN, PI3K and AKT, were measured by qRT-PCR. To gauge the impact of coumarin on the AGS cells, a MTT assay was utilized. A Western blot has been employed to assess variations in PTEN, p-PI3K, and p-AKT expression. The experiment's results showed that AGS viability diminished with increasing doses of coumarin. Compared to the control cells, the cells exposed to coumarin had showed reduced levels of mRNAs which are known targets of the lncRNA BANCR. At the same time, levels of lncRNAs MALAT1 and FER1L4 within coumarin group have been higher comparing to those within control group. Additionally, the Western blot analysis revealed that the coumarin-treated cells expressed lower levels of p-PI3K, PTEN as well as p-AKT compared to control group. This information points to coumarin being a possible option in a treatment regimen for gastric cancer due to its ability to affect lncRNAs and the molecules they target.

The prognostic, diagnostic, and therapeutic impact of Long noncoding RNAs in gastric cancer

Gastric cancer (GC), ranking as the third deadliest cancer globally, faces challenges of late diagnosis and limited treatment efficacy. Long non-coding RNAs (lncRNAs) emerge as valuable treasured targets for cancer prognosis, diagnosis, and therapy, given their high specificity, convenient non-invasive detection in body fluids, and crucial roles in diverse physiological and pathological processes. Research indicates the significant involvement of lncRNAs in various aspects of GC pathogenesis, including initiation, metastasis, and recurrence, underscoring their potential as novel diagnostic and prognostic biomarkers, as well as therapeutic targets for GC. Despite existing challenges in the clinical application of lncRNAs in GC, the evolving landscape of lncRNA molecular biology holds promise for advancing the survival and treatment outcomes of gastric cancer patients. This review provides insights into recent studies on lncRNAs in gastric cancer, elucidating their molecular mechanisms and exploring the potential clinical applications in GC.

A comprehensive review of the role of lncRNAs in gastric cancer (GC) pathogenesis, immune regulation, and their clinical applications

Gastric cancer (GC) is the fifth most common malignant tumor and the third leading cause of cancer-related deaths worldwide. Although numerous studies have been conducted on advanced GC, the molecular mechanisms behind it remain obscure. Long non-coding RNAs (lncRNAs) are a family of RNA transcripts capable of regulating target genes at transcriptional, post-transcriptional, and translational stages. They do this by modifying mRNAs, miRNAs, and proteins. These RNAs are critical regulators of many biological processes, including gene epigenetics, transcription, and post-transcriptional levels. This article highlights recent results on lncRNAs involved in drug resistance, proliferation, migration, angiogenesis, apoptosis, autophagy, and immune response in GC. The potential clinical implications of lncRNAs as biomarkers and therapeutic targets in GC are also discussed.

LncRNA GACAT2 binds with protein PKM1/2 to regulate cell mitochondrial function and cementogenesis in an inflammatory environment

Periodontal ligament stem cells (PDLSCs) are a key cell type for restoring/regenerating lost/damaged periodontal tissues, including alveolar bone, periodontal ligament and root cementum, the latter of which is important for regaining tooth function. However, PDLSCs residing in an inflammatory environment generally exhibit compromised functions, as demonstrated by an impaired ability to differentiate into cementoblasts, which are responsible for regrowing the cementum. This study investigated the role of mitochondrial function and downstream long noncoding RNAs (lncRNAs) in regulating inflammation-induced changes in the cementogenesis of PDLSCs. We found that the inflammatory cytokine-induced impairment of the cementogenesis of PDLSCs was closely correlated with their mitochondrial function, and lncRNA microarray analysis and gain/loss-of-function studies identified GACAT2 as a regulator of the cellular events involved in inflammation-mediated mitochondrial function and cementogenesis. Subsequently, a comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS) and parallel reaction monitoring (PRM) assays revealed that GACAT2 could directly bind to pyruvate kinase M1/2 (PKM1/2), a protein correlated with mitochondrial function. Further functional studies demonstrated that GACAT2 overexpression increased the cellular protein expression of PKM1/2, the PKM2 tetramer and phosphorylated PKM2, which led to enhanced pyruvate kinase (PK) activity and increased translocation of PKM2 into mitochondria. We then found that GACAT2 overexpression could reverse the damage to mitochondrial function and cementoblastic differentiation of PDLSCs induced by inflammation and that this effect could be abolished by PKM1/2 knockdown. Our data indicated that by binding to PKM1/2 proteins, the lncRNA GACAT2 plays a critical role in regulating mitochondrial function and cementogenesis in an inflammatory environment.

p73-regulated FER1L4 lncRNA sponges the oncogenic potential of miR-1273g-3p and aids in the suppression of colorectal cancer metastasis

p73 belongs to the p53 tumor suppressor family and is involved in the suppression of metastasis. However, its specific mechanism of action remains to be elucidated. Long non-coding RNAs portray a crucial role in tumor suppression. We have identified lncRNA FER1L4 as a p73 transcriptional target. The binding of p73 to FER1L4 promoter was established by bioinformatics analysis, luciferase reporter, and ChIP assays. Both FER1L4 and p73 knockdown enhanced the migration and invasion rate of colorectal cancer cells. FER1L4 also plays a critical role in p73-mediated cell-cycle arrest and apoptosis. FER1L4 sponged the expression of miR-1273g-3p, which, in turn, increased PTEN expression, leading to cell-cycle arrest. RNA in situ hybridization revealed the down-regulation of both p73 and FER1L4 expression in a metastatic colon cancer tissue as compared with non-metastatic tissue. Collectively, we impart conclusive proof that p73 exerts its anti-metastatic properties by inducing lncRNA FER1L4 in response to genotoxic stress.

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Long non-coding RNA FER1L4 functions as a direct transcriptional target of p73

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FER1L4 plays a pivotal role in p73-mediated cell-cycle arrest and apoptosis

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FER1L4kd augments colorectal cancer cell proliferation in a p73-dependent manner

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p73-FER1L4 axis sponges miR-1273g-3p and inhibits its oncogenic role

LINC02535 promotes cell growth in poorly differentiated gastric cancer

Background

Abnormal long non‐coding RNA (lncRNA) expression plays important roles in gastric cancer. However, the functions of many lncRNAs in poorly differentiated gastric cancer (PDGC) remain unknown.

Methods

Three sets of paired tissues from patients with PDGC were used, and transcriptome sequencing was performed, followed by the construction and sequencing of a library and mapping of the reads. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and protein‐protein interaction (PPI) networks were analysed, and canonical pathway significance was calculated among the differentially expressed genes (DEGs; p < 0.05). Gene expression in 30 paired PDGC specimens and four cell lines was validated through quantitative PCR. Cell proliferation, migration, invasion, apoptosis, and wound healing were analysed.

Results

A total of 499 upregulated DEGs and 627 downregulated DEGs were identified between peritumoral and gastric cancer tissues. The proportions of positive and negative correlations between LINC02535 and the DEGs were 98.40% and 92.66%, respectively, while the Spearman's correlation coefficient was greater than 0.5. The PPI network showed that approximately 73.15% of the top five genes were directly correlated with LINC02535 according to the STRING database. Based on KEGG analysis, the functions of LINC02535 target genes were enriched in signalling pathways related to cancer cell growth. Furthermore, cell function studies showed that LINC02535 upregulation contributed to cell proliferation, migration, invasion, and wound healing and that its inhibition facilitated cell apoptosis.

Conclusion

LINC02535 expression was upregulated in PDGC and contributed to cell proliferation, migration, invasion and wound healing, whereas its inhibition in PDGC facilitated cell apoptosis.

LncRNA TINCR favors tumorigenesis via STAT3-TINCR-EGFR-feedback loop by recruiting DNMT1 and acting as a competing endogenous RNA in human breast cancer

The long noncoding RNA (lncRNA) TINCR has recently been found to be associated with the progression of human malignancies, but the molecular mechanism of TINCR action remains elusive, particularly in breast cancer. The oncogenic role of TINCR was examined in vitro and in vivo in breast cancer. Next, the interaction between TINCR, DNMT1, and miR-503-5p methylation was explored. Moreover, the mechanism by which TINCR enhances EGFR expression and downstream signaling via an RNA–RNA interaction was comprehensively investigated. Furthermore, upstream transcriptional regulation of TINCR expression by STAT3 was examined by performing chromatin immunoprecipitation. Finally, feedback signaling in the STAT3–TINCR–EGFR downstream cascade was also investigated. TINCR is upregulated in human breast cancer tissues, and TINCR knockdown suppresses tumorigenesis in vitro and in vivo. Mechanistically, TINCR recruits DNMT1 to the miR-503-5p locus promoter, which increases the methylation and suppresses the transcriptional expression of miR-503-5p. Furthermore, TINCR also functions as a competing endogenous RNA to upregulate EGFR expression by sponging miR-503-5p. In addition, TINCR stimulates JAK2–STAT3 signaling downstream from EGFR, and STAT3 reciprocally enhances the transcriptional expression of TINCR. Our findings broaden the current understanding of the diverse manners in which TINCR functions in cancer biology. The newly identified STAT3–TINCR–EGFR-feedback loop could serve as a potential therapeutic target for human cancer.

ADAM10 expression in gastric adenocarcinoma: Results of a curative gastrectomy cohort

Objective:

Gastric cancer is among the most common human cancers with high mortality rates. ADAM10, a member of the ADAM (a disintegrin and metalloproteinase) family has also been found to be associated with gastric carcinoma and has been suggested as a potential therapeutic target. Here, we investigated the association of ADAM10 expression with prognosis in gastric adenocarcinoma patients that underwent gastric resection with D2 lymph node dissection.

Methods:

Total 86 consecutive patients that underwent resection for gastric adenocarcinoma were included. Immunohistochemical ADAM10 expression and its association with clinicopathological parameters were analyzed. Univariate and multivariate analyses and survival analyses were performed using SPSS ver.22.

Results:

High grade tumors, advanced stage tumors and diffuse type tumors showed significantly worse prognosis. A statistically significant association between ADAM10 expression and overall survival (OS) was observed in the univariate analysis, however, this association did not maintain its significance in the multivariate analysis. No statistically significant association was found ADAM-10 expression and clinicopathological parameters.

Conclusion:

Immunohistochemical ADAM10 expression may be used as a prognostic marker in gastric adenocarcinoma, however, introduction of a standardized immunohistochemical scoring system seems to be necessary for evaluation of ADAM10 staining.

Relationship between long non-coding RNA TUG1 and prognosis of patients with gastric carcinoma: A protocol for systematic review and meta-analysis

BACKGROUND

Long non-coding RNA (lncRNA) can predict the prognosis of patients with various cancers. The relationship between lncRNA taurine upregulated gene 1 (TUG1) and the prognosis of patients with gastric carcinoma still needs to be further explored. Therefore, this study attempted to explore the relationship between TUG1 and the prognosis of patients suffering from gastric carcinoma.

METHODS

The database was retrieved from China National Knowledge Infrastructure (CNKI), Chinese Biomedical literature Database (CBM), Chinese Scientific and Journal Database (VIP), Wan Fang database, PubMed, and EMBASE. Hazard ratios (HRs) and its 95% confidence interval (CIs) were applied to assess the prognostic effects of TUG1 on overall survival (OS). RevMan 5.3 software was adopted to perform meta-analysis.

RESULTS

The results of this meta-analysis would be submitted to peer-reviewed journals for publication.

CONCLUSION

This review provided a comprehensive overview of the relationship between TUG1 and the prognosis of patients with gastric carcinoma, and offered recommendations for clinical practices or guidelines.

Long non‑coding RNA JPX promotes gastric cancer progression by regulating CXCR6 and autophagy via inhibiting miR‑197

Long non-coding RNAs (lncRNAs) serve a crucial role in gastric cancer (GC) progression. However, the molecular mechanism underlying lncRNA JPX transcript, XIST activator (JPX) in the tumorigenesis of GC is not completely understood. Reverse transcription-quantitative PCR (RT-qPCR) and western blotting were performed to detect gene expression. A luciferase reporter gene assay was conducted to determine the relationship between microRNA (miR)-197 and JPX or C-X-C motif chemokine receptor 6 (CXCR6). Cell viability, migration and invasion were determined by performing MTT, wound healing and Transwell assays, respectively. The Cancer Genome Atlas database and the RT-qPCR results indicated that JPX expression was upregulated and miR-197 expression was downregulated in patients with GC and in GC cells. Moreover, high JPX expression and low miR-197 expression in patients with GC indicated poor prognosis. miR-197 expression was directly inhibited by JPX. Compared with the short hairpin RNA (sh) negative control (NC) group, NCI-N87 and MKN-45 cells in the shJPX group displayed decreased cell viability and invasion, as well as a wider scratch width. NCI-N87 and MKN-45 cells in the shJPX + miR-197 inhibitor group had increased viability and invasion, but a narrower scratch width compared with the shJPX group. It was also identified that miR-197 directly inhibited CXCR6 expression. miR-197 inhibited Beclin1 protein expression and promoted p62 protein expression. Compared with the NC group, NCI-N87 and MKN-45 cells in the miR-197 mimic group had decreased cell viability and invasion, and a wider scratch width. Enhanced cell viability and invasion, and a narrower scratch width was also observed in the miR-197 mimic + CXCR6 and miR-197 mimic + Beclin1 groups, compared with the miR-197 mimic group. Collectively, the results indicated that lncRNA JPX promoted GC progression by regulating CXCR6 and autophagy via inhibiting miR-197. Furthermore, JPX knockdown regulated GC cell phenotype by promoting miR-197.

Long non-coding RNA signature in gastric cancer

Gastric cancer as a common human malignancy has been associated with aberrant expressions of several coding and non-coding genes. Long non-coding RNAs (lncRNAs) as regulators of gene expressions at different genomic, transcriptomic and post-transcriptomic levels are among putative biomarkers and therapeutic targets in gastric cancer. In the present study, we have searched available literature and listed lncRNAs that are involved in the pathogenesis of gastric cancer. In addition, we discuss associations between expressions of these lncRNAs and tumoral features or risk factors for gastric cancer. Based on the established role of lncRNAs in regulation of genomic stability, cell cycle, apoptosis, angiogenesis and other aspects of cell physiology, the potential of these transcripts as therapeutic targets in gastric cancer should be evaluated in future studies.

Exosomal long noncoding RNA lnc-GNAQ-6:1 may serve as a diagnostic marker for gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most aggressive cancers, with limited early diagnostic measures. Tumor-originated exosomal molecules are regarded as suitable candidates for non-invasive diagnosis. This study aimed to investigate the capacity of exosomal long noncoding RNA lnc-GNAQ-6:1 as a biomarker for early diagnosis of GC.

METHODS

In this study, we collected sera from 43 patients with gastric cancer and 27 healthy subjects, then exosomes were isolated using commercial kits. Particle size analysis, Western bloting and protein-based exosomes quantification were conducted to identify the isolated exosomes and to evaluate its yield and purity. Expression levels of exosomal lnc-GNAQ-6:1 were detected by quantitative reverse transcription PCR (qRT-PCR). The serum concentrations of traditional biomarker (CA72-4, CEA, and CA19-9) were measured via a chemiluminescent detection system.The receiver operating characteristic curve (ROC) and area under curve (AUC) were used to estimate the diagnostic capacity. Furthermore, we analyzed the potential relationship between serum exosomal lnc-GNAQ-6:1 expression and clinicopathological parameters of gastric cancer.

RESULTS

The exosomes extracted in this study exhibited the typical exosome characteristics and purity. Patients with gastric cancer had the higher exosome yield than healthy volunteer. The results of qRT-PCR showed that compared with the healthy control, the expression of lnc-GNAQ-6:1 was significantly lower in the gastric cancer group. The area under the ROC curve is 0.732, which was higher than the diagnostic accuracy of CEA, CA 19-9 and CA72-4. However, the expression level of lnc-GNAQ-6:1 was not correlated with gender, age, tumor metastasis, serum carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), and carbohydrate antigen 72-4(CA72-4).

CONCLUSIONS

Our data demonstrated that serum exosomal lnc-GNAQ-6:1 is lowly expressed in patient with gastric cancer and might be evaluated in larger studies as a new diagnostic marker for gastric cancer.

lncRNA MALAT1 overexpression promotes proliferation, migration and invasion of gastric cancer by activating the PI3K/AKT pathway

Long non-coding RNA (lncRNA) has been implicated in various types of human cancer. However, the role of lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in gastric cancer remains unclear. In the present study, MALAT1 expression was significantly upregulated in gastric tumors compared with adjacent healthy tissue in patients with gastric cancer. Furthermore, MALAT1 plasma expression was higher in patients with gastric cancer compared with healthy controls and was found to have prognostic and diagnostic value independent of patients' lifestyle choices. Cell proliferation assay and Transwell migration and invasion results indicated that the overexpression of MALAT1 resulted in increased proliferation, migration and invasion of gastric cancer cells in vitro, possibly through activation of the phosphoinositide 3-kinase/protein kinase B pathway.

Long non-coding RNA LINC01314 represses cell migration, invasion, and angiogenesis in gastric cancer via the Wnt/β-catenin signaling pathway by down-regulating KLK4

Background

In recent years, gastric cancer (GC) has become a major cause of mortality among various malignancies worldwide with high incidence rates. Long non-coding RNA (lncRNAs) may serve as oncogenes and tumor suppressors in cancers. Therefore, we investigated the effect of LINC01314 on the development of GC cells in relation to the Wnt/β-catenin signaling pathway.

Methods

Microarray data analysis was conducted to screen GC-related differentially expressed lncRNAs, followed by determination of the binding interaction between LINC01314 and kallikrein 4 (KLK4). Human GC cell line SGC-7901 was treated with over-expressed or silenced LINC01314 or KLK4 to investigate the mechanism LINC01314 affecting GC cellular activities. The levels of KLK4, Wnt-1, β-catenin, cyclin D1, N-cadherin and E-cadherin were measured, and cell invasion and migration were evaluated. Next, the tumor weight, micro-vessel density (MVD) and the expression of VEGF-C and VEGFR-3 in transplanted tumors were measured.

Results

LINC01314 was poorly expressed in GC cells and KLK4 was revealed to be a direct target gene of LINC01314. Overexpressed LINC01314 or silencing of KLK4 led to inhibited GC cell migration and invasion, corresponding to decreased Wnt-1, β-catenin, cyclin D1 and N-cadherin while increased E-cadherin. Also, in response to over-expression of LINC01314 or silencing of KLK4, tumor weight and the MVD of transplanted tumors were reduced and angiogenesis was suppressed, which was indicated by down-regulated positive expression of VEGF-C and VEGFR-3.

Conclusion

The findings indicated that over-expression of LINC01314 down-regulated KLK4 to inhibit the activation of the Wnt/β-catenin signaling pathway, thus suppressing migration, invasion, and angiogenesis in GC cells, which provides new insight for the treatment of GC.

Long noncoding RNA STCAT16 suppresses cell growth and its expression predicts prognosis in patients with gastric cancer

Gastric cancer (GC) is a leading cause of cancer‑associated mortality worldwide. Previous studies demonstrated that long noncoding RNAs (lncRNAs) may be dysregulated in GC and may serve important roles in cancer progression. The present study aimed to investigate the role of the novel lncRNA stomach cancer‑associated transcript 16 (STCAT16; Assembly Gene ID G038291) in the development and progression of GC. The present data suggested that the expression level of STCAT16 was decreased in GC tissues. The expression level of STCAT16 was identified to be associated with lymph node and tumour node metastasis stages. Furthermore, the expression level of STCAT16 was identified to be significantly associated with poor survival and prognosis. Knockdown of STCAT16 promoted proliferation, colony formation, migration and invasion of BGC‑823 cells. In contrast, these features were suppressed in AGS cells following overexpression of STCAT16. In vivo, tumour growth was significantly decreased following STCAT16 overexpression. Collectively, the present data suggested that the lncRNA STCAT16 may act as a tumour suppressor and may inhibit GC tumour cell growth and migration. Additionally, the decreased expression level of STCAT16 was identified to be associated with poor prognosis in patients with GC.

LONG-NONCODING RNAs in gastroesophageal cancers

Despite continuing improvements in multimodal therapies, gastro-esophageal malignances remain widely prevalent in the population and is characterized by poor overall and disease-free survival rates. Due to the lack of understanding about the pathogenesis and absence of reliable markers, gastro-esophageal cancers are associated with delayed diagnosis. The increasing understanding about cancer's molecular landscape in the recent years, offers the possibility of identifying 'targetable' molecular events and in particular facilitates novel treatment strategies and development of biomarkers for early stage diagnosis. At least 98% of our genome is actively transcribed into non-coding RNAs encompassing long non-coding RNAs (lncRNAs) constituted of transcripts longer than 200 nucleotides with no protein-coding capacity. Many studies have demonstrated that lncRNAs are functional genomic elements playing pivotal roles in main oncogenic processes. LncRNA can act at multiple levels developing a complex molecular network that can modulate directly or indirectly the expression of genes involved in tumorigenesis. In this review, we focus on lncRNAs as emerging players in gastro-esophageal carcinogenesis and critically assess their potential as reliable noninvasive biomarkers and in next generation targeted therapies.

LncRNA SNHG5 affects cell proliferation, metastasis and migration of colorectal cancer through regulating miR-132-3p/CREB5

We aimed at the effects of long non-coding RNA (lncRNA) SNHG5 on proliferation, metastasis and migration of colorectal cancer (CRC) cells. We also investigated regulatory relationships among miR-132-3p, SNHG5 and CREB5 and their roles in CRC. 25 pairs of samples containing CRC tissues and matched para-tumor tissues were obtained to examine SNHG5, miR-132-3p and CREB5 expression by qRT-PCR or Western blot. The targeted relationship between miR-132-3p and SNHG5 or CREB5 was confirmed by dual luciferase report assay as well as RNA pull down assay. The expression of SNHG5, miR-132-3p and CREB5 in CRC cells were regulated by cell transfection. CRC cellular proliferation was assayed by CCK-8 and meanwhile flow cytometry was adopted to observe apoptosis. Metastasis and migration of CRC cells were determined respectively by means of Transwell assay and scratch test. The effects of SNHG5 on CRC were researched in vivo, too. SNHG5 or CREB5 was up-regulated in CRC tissues and cells, whereas miR-132-3p was down-regulated. Overexpression of SNHG5 and CREB5 resulted in the enhancement of proliferation, metastasis, migration and the inhibition of apoptosis in CRC cells, while miR-132-3p led to the opposite result. LncRNA SNHG5 promoted proliferation, migration and metastasis of CRC cells but inhibited apoptosis by modulating miR-132-3p/CERB5.

Non-target Genes Regulate miRNAs-Mediated Migration Steering of Colorectal Carcinoma

MicroRNAs (miRNAs) trigger a two-layer regulatory network directly or through transcription factors and their co-regulators. Unlike miR-375, the role of miR-145 and miR-224 in inhibiting or driving cancer cell migration is controversial. This study is a step towards addressing the potential of miR-375, miR-145 and miR-224 expression modulation to inhibit colorectal carcinoma (CRC) cells migration in vitro through regulation of non-target genes VEGFA, TGFβ1, IGF1, CD105 and CD44. Transwell migration assay results revealed a significant subdue of migration ability of cells transfected with miR-375 and miR-145 mimics and miR-224 inhibitor. Real time PCR data showed that expression of VEGFA, TGFβ1, IGF1, CD105 and CD44 was downregulated as a consequence of exogenous re-expression of miR-375 and inhibition of miR-224. On the other hand, ectopic expression of miR-145 did not affect VEGFA, TGFβ1 and CD44 expression, while it elevated CD105 and suppressed IGF1 expression. MAP4K4, a predicted target of miR-145, was validated as a target that could play a role in miR-145-mediated regulation of migration. At mRNA level, no change was observed in expression of MAP4K4 in cells with restored expression of miR-145, while western blotting analysis revealed a 25% reduction of protein level. By applying luciferase reporter assay, a significant decrease in luciferase activity was observed, supporting that miR-145 directly target 3' UTR of MAP4K4. The study highlighted the involvement of non-target genes VEGFA, TGFβ1, IGF1, CD105 and CD44 in mediating anti- and pro-migratory effect of miR-375 and miR-224, respectively, and validated MAP4K4 as a direct target of anti-migratory miR-145.

Emerging role of long non-coding RNA in the development of gastric cancer

Gastric cancer is a common, worldwide malignancy and has a poor prognosis due to late diagnosis. Long non-coding RNAs (lncRNAs) are a significant subtype of RNA molecules with a length longer than 200 nucleotides (nt) that rarely encode proteins. In recent decades, deregulation of lncRNAs has been shown to be involved in tumorigenesis and tumor progression in various human carcinomas, including gastric cancer. Accumulating evidence has shown that some lncRNAs may function as diagnostic biomarkers or therapeutic targets for gastric cancer. Thus, exploring the specific functions of lncRNAs will help both gain a better understanding of the pathogenesis and develop novel treatments for gastric cancer. In this review, we highlight the expression and functional roles of lncRNAs in gastric cancer, and analyze the potential applications of lncRNAs as diagnostic markers and therapeutic targets.

Long non-coding RNAs involved in metastasis of gastric cancer

Gastric cancer (GC) is one of the most frequently diagnosed malignant diseases. The molecular mechanisms of metastasis remain unclear. Recently, studies have shown that long non-coding RNAs (lncRNAs) play critical roles in metastasis. Therefore, deeper understanding of this mechanism could provide potential diagnostic tools and therapeutic targets for metastatic GC. This review focuses on dysregulated lncRNAs in GC metastases. Due to the identification of multiple diverse mechanisms involved in GC metastasis, we classified them into seven categories, including lncRNAs related to epithelial-mesenchymal transition, regulation of degradation of extracellular matrix, angiopoiesis, vasculogenic mimicry, and immunologic escape. As the TNM stage is pivotal for evaluating the severity and prognosis of GC patients, we summarize the lncRNAs relevant to lymphatic metastasis, distant metastasis and TNM classification. This review summarizes the lncRNAs related to metastasis, which may provide insight into the mechanisms, and provide potential markers for prognostic prediction and monitoring the relapse of GC.

Long non-coding RNAs in the gastric juice of gastric cancer patients

Differently from other digestive malignancies, gastric cancer (GC) carcinogenesis seems more heterogeneous and unclear. This entails failing in identification of reliable serum tumor markers for screening early GC (EGC) as well as persisting ominous prognosis of this disease. Recently, investigation of human noncoding genome, especially long noncoding molecules (lncRNAs), has provided promising data. As for GC, however, since the current information on GC-specific lncRNAs is still scarce and comes largely from analyses performed on tissue or serum of affected patients, we decided to review the current literature dealing with expression of such molecules in the gastric juice (GJ) of GC patients. In the case of GC, in fact, several cytological and molecular works have already demonstrated GJ to be an interesting biological material for improving clinicopathologic and prognostic knowledge of this cancer. For this review, we burrowed into the literature on lncRNAs expressed in GJ of GC patients. PubMed, Science Direct, Scopus, Web of Science, Google Scholar and ResearchGate were the search engines entertained. As of 2018, only seven studies have been reported. LINC00152, AA174084, UCA1, RMRP, ABHD11-AS1, LINC00982 and H19 were the GJ lncRNAs examined. Following our review, we can conclude that, due to their high specificity and reliability, GJ lncRNAs should deserve a prominent role in the field of GC research: importantly, they could be used for screening EGC, ameliorating the existing methods of staging (which are still far from being completely accurate), improving the prognostic capacity of the current diagnostic armamentarium and, finally, providing new and valuable therapeutic targets.

Identification of differential expression lncRNAs in gastric cancer using transcriptome sequencing and bioinformatics analyses

The current study aimed to identify novel long non-coding RNAs (lncRNAs) associated with gastric cancer (GC). Transcriptome sequencing of the lncRNAs and mRNAs from GC tissues and normal adjacent tissues was performed. The data were analyzed using bioinformatics analysis, specifically analysis of differentially expressed lncRNAs and mRNA, target gene prediction and functional enrichment analysis. A total of 1,181 differentially expressed mRNA and 390 differentially expressed lncRNAs were identified. The targets of upregulated lncRNAs were significantly enriched in functions associated with collagen fibril organization, whereas the downregulated lncRNA were significantly associated with ion transmembrane transport and regulation of membrane potential. A total of 7 lncRNAs were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Following RT-qPCR validation, AC016735.2, AP001626.1, RP11-400N13.3 and RP11-243M5.2 were considered to be consistent with the prediction of the bioinformatics analysis. Transcriptome sequencing and RT-qPCR experiments identified 4 lncRNAs, including AC016735.2, AP001626.1, RP11-400N13.3 and RP11-243M5.2 to have an important role in the carcinogenesis of GC.

Decoding the Emerging Patterns Exhibited in Non-coding RNAs Characteristic of Lung Cancer with Regard to their Clinical Significance

Lung cancer continues to be the leading topic concerning global mortality rate caused by can-cer; it needs to be further investigated to reduce these dramatic unfavorable statistic data. Non-coding RNAs (ncRNAs) have been shown to be important cellular regulatory factors and the alteration of their expression levels has become correlated to extensive number of pathologies. Specifically, their expres-sion profiles are correlated with development and progression of lung cancer, generating great interest for further investigation. This review focuses on the complex role of non-coding RNAs, namely miR-NAs, piwi-interacting RNAs, small nucleolar RNAs, long non-coding RNAs and circular RNAs in the process of developing novel biomarkers for diagnostic and prognostic factors that can then be utilized for personalized therapies toward this devastating disease. To support the concept of personalized medi-cine, we will focus on the roles of miRNAs in lung cancer tumorigenesis, their use as diagnostic and prognostic biomarkers and their application for patient therapy.

Clinical significance of the long noncoding RNA RP11-19P22.6-001 in gastric cancer

BACKGROUND

Long non-coding RNAs (lncRNAs) play roles in carcinogenesis; however, the significance of most lncRNAs in gastric cancer is unclear.

OBJECTIVE

To explore the diagnostic value of the long noncoding RNA RP11-19P22.6-001 in gastric cancer.

METHODS

RP11-19P22.6-001 levels in gastric cancer tissues and paired non-tumor tissues were analyzed by quantitative reverse transcription-polymerase chain reaction. Since RP11-19P22.6-001 acts in cis to regulate nitric oxide synthase 2 (NOS2), we also analyzed NOS2 expression and its correlation with gastric cancer. Finally, to analyze the potential diagnostic values of RP11-19P22.6-001, a receiver operating characteristic (ROC) curve was constructed.

RESULTS

RP11-19P22.6-001 expression was significantly downregulated in 70.91% (78/110) of gastric cancer tissues compared to that of adjacent normal tissues. However, NOS2 was upregulated in 75.45% (83/110) of gastric cancer tissues. RP11-19P22.6-001 expression levels were associated with invasion, lymph node metastasis, and TNM stage. The areas under the ROC curves (AUC) were 0.662 and 0.671 for RP11-19P22.6-001 and NOS2, respectively. More importantly, the combined use of these parameters increased the AUC to 0.704.

CONCLUSIONS

RP11-19P22.6-001 and NOS2 may be new biomarkers for the diagnosis and prognosis of gastric cancer. The combined use of lncRNAs and their target genes may be a promising method to increase the diagnostic value of lncRNAs in cancer.

Long noncoding RNAs in gastric cancer carcinogenesis and metastasis

Recent studies of the human transcriptome, most prominently by the ENCyclopedia Of DNA Elements project, have revealed an unexpected number of noncoding RNAs (ncRNAs). Long noncoding RNAs (lncRNAs) are typically referred to a heterogeneous group of polyadenylated long ncRNAs, with a length of > 200 nt. LncRNAs constitute an integral part of tumor biology, with many lncRNAs discovered to be aberrantly expressed in various cancer types. They are involved in many aspects of cancer pathogenesis from its initiation to progression, metastasis and treatment response. Gastric cancer (GC) is the third leading cause of cancer death worldwide. Despite the current improvements of life expectancy and survival rate, most of the patients are diagnosed when their cancer has been progressed to advanced stages. Therefore, unraveling the molecular mechanisms of GC to find early-stage biomarkers is urgent. As the list of lncRNAs with deregulated expression in GC is steadily expanding, these molecules offer a source for developing GC-specific biomarkers. In this review, we will present and discuss those lncRNAs whose expression has been shown to be deregulated in GC.

Elementary screening of lymph node metastatic-related genes in gastric cancer based on the co-expression network of messenger RNA, microRNA and long non-coding RNA

Gastric cancer (GC) is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. The high mortality might be attributed to delay in detection and is closely related to lymph node metastasis. Therefore, it is of great importance to explore the mechanism of lymph node metastasis and find strategies to block GC metastasis. Messenger RNA (mRNA), microRNA (miRNA) and long non-coding RNA (lncRNA) expression data and clinical data were downloaded from The Cancer Genome Atlas (TCGA) database. A total of 908 differentially expressed factors with variance >0.5 including 542 genes, 42 miRNA, and 324 lncRNA were screened using significant analysis microarray algorithm, and interaction networks were constructed using these differentially expressed factors. Furthermore, we conducted functional modules analysis in the network, and found that yellow and turquoise modules could separate samples efficiently. The groups classified in the yellow and turquoise modules had a significant difference in survival time, which was verified in another independent GC mRNA dataset (GSE62254). The results suggested that differentially expressed factors in the yellow and turquoise modules may participate in lymph node metastasis of GC and could be applied as potential biomarkers or therapeutic targets for GC.

Long non-coding RNA AC026166.2-001 inhibits cell proliferation and migration in laryngeal squamous cell carcinoma by regulating the miR-24-3p/p27 axis

Long non-coding RNA (lncRNA) AC026166.2-001 was found to be down-regulated in laryngeal squamous cell carcinoma (LSCC) tissues and metastatic neck lymph nodes. Decreased AC026166.2-001 was associated with poorer prognosis and may act as a novel biomarker for LSCC patients. In this study, AC026166.2–001 was overexpressed by a lentivirus vector and down-regulated by a small interfering RNA (siRNA). The results of real-time cell analysis (RTCA) and a plate colony formation assay showed that AC026166.2–001 inhibited LSCC cell proliferation and the clone-forming capacity. Cell cycle distribution and related protein changes were measured by flow cytometry. AC026166.2–001 arrested the cell cycle at the G1 phase and induced apoptosis. In addition, AC026166.2–001 decreased cell migration as measured by wound healing assays and transwell migration assays. Moreover, luciferase reporter assay and Western blotting results suggested that AC026166.2–001 acts as a sponge of miR-24-3p and regulates the expression of p27 and cyclin D1. The in vivo results showed that AC026166.2–001 significantly suppressed the growth of LSCC xenografts and promoted apoptosis. We validated the molecular mechanisms underlying AC026166.2–001 in LSCC. This is the first report of AC026166.2–001 acting as a tumor suppressor in LSCC by regulating the miR-24-3p/p27 axis.

LncRNA-RMRP promotes carcinogenesis by acting as a miR-206 sponge and is used as a novel biomarker for gastric cancer

Long noncoding RNAs (lncRNAs) play crucial roles in tumorigenesis. However, the mechanisms of most lncRNAs in cancers are largely unknown. Because the RNA component of mitochondrial RNA processing endoribonuclease (RMRP) is one of the dysregulated lncRNAs in gastric cancer, this study explored its molecular mechanisms in carcinogenesis. RMRP levels in 792 tissues, plasma and gastric juices from patients with various stages of gastric tumorigenesis were analyzed by quantitative reverse transcription-polymerase chain reaction. Overexpression and RNA interference were used to manipulate RMRP expression by RMRP expression vector and small interfering RNAs, respectively. Its mechanisms were evaluated by flow cytometry, real-time cell analysis, plate colony formation assays, and xenograft models. RMRP levels in tissue, plasma and gastric juices from patients with gastric cancer were significantly different from those from controls. Its levels were significantly associated with Borrmann type and metastasis. Plasma and gastric juice RMRP had higher sensitivity and specificity than commonly used markers (such as carcinoembryonic antigen and carbohydrate antigen 19-9). Knockdown of RMRP significantly inhibited cell proliferation in vitro and in vivo, whereas overexpression of RMRP promoted cell growth. Acting as a miR-206 sponge, RMRP modulated cell cycle by regulating Cyclin D2 expression. RMRP plays a crucial role in gastric cancer occurrence and can be used as a novel biomarker for gastric cancer.

Comprehensive analysis of a novel four-lncRNA signature as a prognostic biomarker for human gastric cancer

Emerging evidence indicates that long non-coding RNAs (lncRNAs) play a crucial role in predicting survival for gastric cancer (GC) patients. This study aims to identify a lncRNA-related signature for evaluating the overall survival of 379 GC patients from The Cancer Genome Atlas (TCGA) database. The associations between survival outcome and the expression of lncRNAs were evaluated by the univariate and multivariate Cox proportional hazards regression analyses. Four lncRNAs (LINC01018, LOC553137, MIR4435-2HG, and TTTY14) were identified as significantly correlated with overall survival. These four lncRNAs were gathered as a single prognostic signature. There was a significant positive correlation between GC patients with low-risk scores and overall survival (P = 0.001). Further analysis suggested that the prognostic value of this four-lncRNA signature was independent in clinical features. Gene set enrichment analysis found that these four lncRNAs were correlated with several molecular pathways of the tumor. Our study indicates that this novel lncRNA expression signature may be a useful biomarker of the prognosis for GC patients, based on bioinformatics analysis.

Low expression of hsa_circ_0006633 in human gastric cancer and its clinical significances

Circular RNAs are new type of endogenous RNAs, which play an important role in the regulation of gene expression and indicate a great capacity in clinical diagnosis and treatments of diseases. However, the role of circular RNAs in gastric cancer remains unknown. In this study, we chose hsa_circ_0006633 as the target circular RNA and measured its levels in human gastric cancer tissues, plasma, and gastric cell lines by real-time quantitative reverse transcription polymerase chain reaction. Hsa_circ_0006633 levels at multiple stages of gastric tumorigenesis were then explored, and its relationships with clinicopathological features were analyzed as well. We found that the expression levels of hsa_circ_0006633 in four gastric cancer cell lines, HGC-27, SGC-7901, MGC-803, and AGS, were downregulated than those in normal gastric mucosal epithelial cell line GES-1. Then, we further detected that it was downregulated in 79.2% (76/96) gastric cancer tissues compared with the adjacent non-tumorous tissues. The lower expression of hsa_circ_0006633 was associated with cancer distal metastasis ( p = 0.037) and tissue carcinoembryonic antigen level ( p = 0.041). In addition, hsa_circ_0006633 expression was significantly decreased in gastritis and dysplasia tissues comparing with the healthy control. Moreover, plasma hsa_circ_0006633 levels were significantly increased in gastric cancer compared with healthy control. Our data imply that hsa_circ_0006633 may play an important role in gastric carcinogenesis and is also a potential biomarker for screening gastric cancer.

Decreased expression of hsa_circ_0001895 in human gastric cancer and its clinical significances

Circular RNAs are a special class of endogenous RNAs characterized by jointing 3' and 5' ends together via exon or intron circularization. Recent studies found that circular RNAs are involved in the development of some human diseases. However, little is known about their roles in human gastric cancer. In this study, we chose hsa_circ_0001895 as a targeted circRNA to investigate its clinical significances in gastric cancer patients. Hsa_circ_0001895 expression levels in five gastric cancer cell lines and 257 specimens of tissues were measured by real-time quantitative reverse transcription polymerase chain reaction. Then, the potential relationship between hsa_circ_0001895 expression levels and patients' clinicopathological factors was investigated. A receiver operating characteristic curve was constructed for evaluating the diagnostic value of hsa_circ_0001895. Hsa_circ_0001895 expression levels in five detected gastric cancer cell lines (AGS, BGC-823, HGC-27, MGC-803, and SGC-7901) were all significantly downregulated than those in normal gastric epithelial GES-1 cells. Besides, compared with healthy control tissues, it was downregulated not only in 69.8% (67/96) gastric cancer tissues but also in gastric precancerous lesions. Moreover, hsa_circ_0001895 expression levels were significantly correlated with cell differentiation, Borrmann type, and tissue carcino-embryonic antigen expression. Our results suggested that hsa_circ_0001895 may play crucial roles during gastric cancerogenesis and is a potential biomarker for clinical prognosis prediction.

Molecular mechanisms of long noncoding RNAs on gastric cancer

Long noncoding RNAs (lncRNAs) are non-protein coding transcripts longer than 200 nucleotides. Aberrant expression of lncRNAs has been found associated with gastric cancer, one of the most malignant tumors. By complementary base pairing with mRNAs or forming complexes with RNA binding proteins (RBPs), some lncRNAs including GHET1, MALAT1, and TINCR may mediate mRNA stability and splicing. Other lncRNAs, such as BC032469, GAPLINC, and HOTAIR, participate in the competing endogenous RNA (ceRNA) network. Under certain circumstances, ANRIL, GACAT3, H19, MEG3, and TUSC7 exhibit their biological roles by associating with microRNAs (miRNAs). By recruiting histone-modifying complexes, ANRIL, FENDRR, H19, HOTAIR, MALAT1, and PVT1 may inhibit the transcription of target genes in cis or trans. Through these mechanisms, lncRNAs form RNA-dsDNA triplex. CCAT1, GAPLINC, GAS5, H19, MEG3, and TUSC7 play oncogenic or tumor suppressor roles by correlated with tumor suppressor P53 or onco-protein c-Myc, respectively. In conclusion, interaction with DNA, RNA and proteins is involved in lncRNAs' participation in gastric tumorigenesis and development.

Plasma lncRNA-GACAT2 is a valuable marker for the screening of gastric cancer

Long non-coding RNAs (lncRNAs) are crucial in contributing to gastric tumorigenesis and development. However, the diagnostic value of the majority of lncRNAs in gastric cancer (GC) are not clear. The present study investigated the diagnostic value of gastric cancer associated transcript 2 (GACAT2), a lncRNA that is aberrantly expressed in GC tissues. A total of 343 plasma samples from 80 healthy individuals, 29 patients with gastric dysplasia (GD) and 117 paired preoperative and postoperative patients with GC were collected. Plasma GACAT2 levels were subsequently measured by reverse transcription-quantitative polymerase chain reaction. Finally, the associations between plasma GACAT2 levels and various clinicopathological features of patients with GC were assessed. The results demonstrated that plasma GACAT2 levels in preoperative patients with GC were significantly higher than those in the postoperative group (P=0.031). Compared with healthy individuals, plasma GACAT2 levels were significantly increased in patients with GD (P<0.001) and preoperative patients with GC (P=0.040). Moreover, the individual relative changes of plasma GACAT2 expression following surgery were significantly associated with lymphatic metastasis (P=0.034), distal metastasis (P=0.035) and perineural invasion (P=0.039). Therefore, the results of the current study suggest that plasma-based GACAT2 may be developed as a tumor marker to screen and predict the prognosis of GC patients.

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.

LncRNA-ATB mediated E-cadherin repression promotes the progression of colon cancer and predicts poor prognosis

BACKGROUND

Long non-coding RNA-activated by TGF-β (lncRNA-ATB) promotes the invasion-metastasis cascade in hepatocellular carcinoma via downregulating E-cadherin (E-cad) and inducing epithelial-to- mesenchymal transition (EMT) and is clinically significant in human colon cancer. However, its molecular mechanisms in colon cancer progression remain unclear. This study aimed to elucidate the role of lncRNA-ATB and its clinical value in colon cancer.

METHODS

Expression levels of lncRNA-ATB in colon cancer tissues and colon cancer cell lines were evaluated using quantitative real-time polymerase chain reaction. The clinicopathological significance and prognostic value of lncRNA-ATB were investigated, and roles of lncRNA-ATB in regulating E-cad and other EMT-related markers expression and colon cancer progression were evaluated in vitro. Expression levels of lncRNA-ATB and E-cad in human plasma were evaluated.

RESULTS

Long non-coding RNA-activated by TGF-β was upregulated in colon cancer tissues compared with adjacent mucosa (P < 0.001). LncRNA-ATB levels were also higher in metastatic cancer tissues (P < 0.001). Among the three highly invasive colon cancer cell lines, lncRNA-ATB levels were relatively higher with concurrent low levels of E-cad compared with levels in the three low-invasive cell lines. LncRNA-ATB expression correlated with pN stage (P < 0.01) and American Joint Committee on Cancer stage (P < 0.01). Striking differences were observed in overall survival and disease-free survival in cases with both high lncRNA-ATB expression and low E-cad expression. Reduction of lncRNA-ATB increased expression of epithelial markers E-cad, ZO-1, and decreased expression of mesenchymal markers ZEB1 and N-cadherin (N-cad), and significantly influenced colon cancer cell progression. Plasma lncRNA-ATB was upregulated in colon cancer patients one month after surgery (P < 0.05).

CONCLUSIONS

Long non-coding RNA-activated by TGF-β may act on colon tumorigenesis by suppressing E-cad expression and promoting EMT process, and lncRNA-ATB inhibition may provide a promising therapeutic option for suppressing colon cancer progression.

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.

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.

Long noncoding RNAs as potential biomarkers in gastric cancer: Opportunities and challenges

Gastric cancer (GC) is a major threat to human health, and its prognosis is poor due to the lack of appropriate biomarkers. LncRNAs are a group of non-protein-coding RNAs that regulate gene expression at the transcriptional or posttranscriptional level. LncRNAs play essential roles in GC initiation and development in the same way as oncogenes or tumour suppressor genes. Recent investigations have revealed that lncRNAs are often aberrantly expressed in GC; are involved in cell proliferation, apoptosis, migration and invasion; and correlate with the malignant phenotype of GC. LncRNAs, especially the lncRNAs present in the blood and gastric juice, show potential value as biomarkers for the diagnosis of GC or for determining disease prognosis. However, there are still many challenges to be faced before lncRNAs can be used in clinical applications. In this review, we summarise lncRNAs as the potential biomarkers for GC and the current challenges associated with the clinical application.

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.

Expression and clinical significance of long non-coding RNA HNF1A-AS1 in human gastric cancer

BACKGROUND

Increasing evidence has demonstrated that long non-coding RNAs (lncRNAs) play essential roles in the occurrence and development of human cancers, including gastric cancer (GC). However, the functional and clinical significance of lncRNAs are still poorly understood.

METHODS

In this study, the expression of LncRNA HNF1A antisense RNA 1 (HNF1A-AS1) was first examined by lncRNAs microarray analysis in 6 GC tissues, and was then further verified by real-time quantitative reverse transcription PCR (qRT-PCR) both in 3 GC cell lines and 161 cases of GC tissues. We also evaluated the association between HNF1A-AS1 expression and clinicopathological features of patients with GC.

RESULTS

LncRNAs microarray analysis results exhibited that HNF1A-AS1 was downregulated in GCs tissues (mean fold change 2.06, p < 0.05), which was further confirmed by qRT-PCR. The results from qRT-PCR showed that the expression of HNF1A-AS1 was not only downregulated in three GC cell lines (AGS, BGC-823, and MKN-45) relative to that in a normal gastric mucosal epithelial cell line (GES-1), but also decreased in GC tissues relative to that in paired adjacent non-neoplastic tissues (low expression, 94 of 161; low expression rate, 58.38%). Furthermore, low HNF1A-AS1 expression was associated with tumor size/diameter (p = 0.005, multivariate analysis), levels of serum carcinoembryonic antigen (CEA), and carbohydrate antigen 19-9 (CA19-9), and RRM1 expression in tissue samples (p = 0.028, p = 0.009, and p = 0.006, respectively).

CONCLUSIONS

Taken together, our data indicate that lncRNA HNF1A-AS1 may be a regulator of GC, and thus, it may have potential as a novel biomarker and treatment target for this type of cancer.

Long non-coding RNA Fer-1-like protein 4 suppresses oncogenesis and exhibits prognostic value by associating with miR-106a-5p in colon cancer

Novel long non-coding RNA Fer-1-like protein 4 (FER1L4) has been confirmed to play crucial regulatory roles in tumor progression. It exerts an impact on tumor suppression and functions as a competing endogenous RNA (ceRNA) by sponging miR-106a-5p in gastric cancer. However, its clinical significance in colon cancer is completely unknown. The aim of the present study was to annotate the role of FER1L4 and its clinical value in colon cancer. The results showed the aberrant expression of FER1L4 and miR-106a-5p in colon cancer tissues. In addition, significant negative correlation between FER1L4 and miR-106a-5p expression levels was observed. Among the colon cancer cell lines, FER1L4 levels were relatively lower, with concurrent high levels of miR-106a-5p. Restoration of FER1L4 decreased the expression of miR-106a-5p, and had a significant influence on colon cancer cell proliferation, migration and invasion. The FER1L4 expression was correlated with depth of tumor invasion, lymph node metastasis, vascular invasion and clinical stage. Moreover, striking differences in overall survival and disease-free survival were observed for the cases with both low FER1L4 expression and high miR-106a-5p expression compared with cases with high FER1L4 expression and low miR-106a-5p expression. Circulating FER1L4 and miR-106a-5p levels were decreased and increased, respectively, in colon cancer patients after surgery. Our findings indicated that FER1L4 could exert a tumor suppressive impact on colon cancer, which at least, in part, through suppressing miR-106a-5p expression, and depletion of FER1L4, alone or combined with overexpression of miR-106a-5p, is predictive of poor prognosis in colon cancer and may play a crucial role in cancer prevention and treatment.

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.

Long Noncoding RNA in Digestive Tract Cancers: Function, Mechanism, and Potential Biomarker

Digestive tract cancers (DTCs) are a leading cause of cancer-related death worldwide. Current therapeutic tools for advanced stage DTCs have limitations, and patients with early stage DTCs frequently have a missed diagnosis due to shortage of efficient biomarkers. Consequently, it is necessary to develop novel biomarkers for early diagnosis and novel therapeutic targets for treatment of DTCs. In recent years, long noncoding RNAs (lncRNAs), a class of noncoding RNAs with >200 nucleotides, have been shown to be aberrantly expressed in DTCs and to have an important role in DTC development: the expression profiles of lncRNAs strongly correlated with poor survival of patients with DTCs, and lncRNAs acted as oncogenes or tumor suppressor genes in DTC progression. In this review, we summarized the functional lncRNAs and expounded on their regulatory mechanisms in DTCs.

A Long Non-coding RNA Activated by Transforming Growth Factor-β is an Independent Prognostic Marker of Gastric Cancer

BACKGROUND

A recent study reported that long non-coding RNA activated by TGF-β (lncRNA-ATB) induced epithelial-mesenchymal transition (EMT) through the transforming growth factor-β (TGF-β)/miR-200s/ZEB axis in hepatocellular carcinoma. Herein, we focused on the clinical significance of lncRNA-ATB in gastric cancer (GC) patients.

MATERIALS AND METHODS

Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was performed to examine expression of lncRNA-ATB, miR-200b, and miR-200c in GC tissues (n = 183). Patients were divided into high and low lncRNA-ATB expression groups using a cutoff of lncRNA-ATB/GAPDH ≥0.60 or <0.60 to determine the clinicopathological significance of lncRNA-ATB in GC. Moreover, we evaluated the expression of TGF-β, lncRNA-ATB, miR-200s, and ZEB1 in GC cell lines by qRT-PCR. GC cell lines were treated by recombinant TGF-β1 or TGF-β receptor inhibitor to examine morphologic changes and genetic alterations, such as lncRNA-ATB, miR-200s, and ZEB1 levels, with respect to the EMT phenotype.

RESULTS

The high lncRNA-ATB group experienced a lower overall survival rate compared with the low lncRNA-ATB group, and multivariate analysis indicated that lncRNA-ATB was an independent prognostic factor (hazard ratio 3.50; 95 % CI 1.73-7.44; p = 0.0004). miR-200c levels were lower and ZEB1 levels were higher in the high lncRNA-ATB group than in the low lncRNA-ATB group. Treatment with TGF-β in GC cell lines resulted in morphological EMT changes, upregulation of lncRNA-ATB and ZEB1, and downregulation of miR-200c and CDH1. SB431542 reduced lncRNA-ATB expression.

CONCLUSION

LncRNA-ATB plays an important role in EMT to promote invasion and metastasis through the TGF-β/miR-200s/ZEB axis, resulting in a poor prognosis in GC. LncRNA-ATB is a novel biomarker of lncRNA, indicative of a poor prognosis in GC patients.

Increased expression of LncRNA BANCR is associated with clinical progression and poor prognosis in gastric cancer

Long non-coding RNAs (lncRNAs), emerging non-coding RNAs, have been proved to serve as a critical role in the proliferation, metastasis apoptosis of gastric cancer. However little is known about the clinical significance of BRAF-activated non-coding RNA (BANCR) in gastric cancer. The aim of our study is to identify the clinical value of BANCR in gastric cancer patients. Expression of BANCR was analyzed in one hundred and eighty-four gastric cancer samples using Real-time PCR. In our results, the expression of BANCR was increased in gastric cancer tissues compared with paired adjacent normal tissues. Moreover, high expression of BANCR was positively associated with clinical stage, tumor depth, lymph node metastasis and distant metastasis in gastric cancer patients. In survival analysis, high expression of BANCR was an independent unfavorable prognostic factor in gastric cancer patients. In summary, overexpression of BANCR acts as an unfavorable prognostic biomarker in gastric cancer patients.

LncRNAs and neoplasia

Long noncoding RNAs are emerging as new mediators of tumorigenesis by virtue of their various functions and their capacity to induce different mechanisms as a result of their wide spectrum of interactions. They play critical roles in a broad range of cellular processes including regulation of gene expression, imprinting, chromatin modification, transcription and posttranslational processing. Expression and activity of lncRNAs are deregulated in several types of human cancer. Impairment of lncRNA activity may affect key components of the cellular gene regulatory networks and is associated with deregulation of a large number of cellular oncogenic pathways. LncRNAs are also being evaluated as diagnostic and prognostic biomarkers and may provide targets for potential therapeutic applications. An improved understanding of the roles played by lncRNAs in cancer will lead to more effective therapeutic strategies. In this review we summarize the current knowledge on lncRNAs and their function as mediators of tumor development.

MALAT2-activated long noncoding RNA indicates a biomarker of poor prognosis in gastric cancer

The purpose of this study is to investigate the role of the long noncoding RNA metastasis associated lung adenocarcinoma transcript 2 (MALAT2) in the prognosis of stage II/III gastric cancer (GC) patients. The expression of MALAT2 was evaluated in cancer tissues from 146 stage II/III GC patients undergoing radical resection and 60 paired normal samples using quantitative real-time reverse transcriptase PCR. Differences in the expression of MALAT2 between 23 GC and paired normal colonic mucosa samples were analysed with the Wilcoxon test. Relationships between the expression level of MALAT2, patient clinico-pathological parameters and disease-free survival and overall survival were analysed using the uni-variate Kaplan-Meier method and the multivariate COX regression model. The quantitative polymerase chain reaction results showed that MALAT2 was frequently over-expressed in cancer tissues and this over-expression was found to significantly correlate with lymph node metastasis and tumor stage. The ectopic expression of MALAT2 contributed to the migration of human GC SGC-7901 cells, whereas knockdown of MALAT2 inhibited the migration of the SGC-7901 cells in vitro. Further investigation into the underlying mechanisms responsible for the migratory effects revealed that MALAT2 induced the epithelial-mesenchymal transition (EMT) through an MEK/extracellular signal-regulated kinase-dependent mechanism as treatment with the MEK inhibitor, U0126, decreased migration and reversed the EMT in the MALAT2 over-expressed SGC-7901 cells. The expression of MALAT2 is upregulated in GC tissues, and a higher expression level of MALAT2 might serve as a negative prognostic marker in stage II/III GC patients which implies the potential application of MALAT2 in the therapeutic treatment of GC.Cancer Gene Therapy advance online publication, 27 February 2015; doi:10.1038/cgt.2015.6.