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BackgroundAccumulating evidence indicates that the long non-coding RNA HOTAIR plays a critical role in cancer progression and metastasis. However, the overall biological role and clinical significance of HOTAIR in gastric carcinogenesis remains largely unknown.MethodsHOTAIR expression was measured in 78 paired cancerous and noncancerous tissue samples by real-time PCR. The effects of HOTAIR on gastric cancer cells were studied by overexpression and RNA interference approaches in vitro and in vivo. Insights of the mechanism of competitive endogenous RNAs (ceRNAs) were gained from bioinformatic analysis, luciferase assays and RNA binding protein immunoprecipitation (RIP). The positive HOTAIR/HER2 interaction was identified and verified by immunohistochemistry assay and bivariate correlation analysis.ResultsHOTAIR upregulation was associated with larger tumor size, advanced pathological stage and extensive metastasis, and also correlated with shorter overall survival of gastric cancer patients. Furthermore, HOTAIR overexpression promoted the proliferation, migration and invasion of gastric carcinoma cells, while HOTAIR depletion inhibited both cell invasion and cell viability, and induced growth arrest in vitro and in vivo. In particular, HOTAIR may act as a ceRNA, effectively becoming a sink for miR-331-3p, thereby modulating the derepression of HER2 and imposing an additional level of post-transcriptional regulation. Finally, the positive HOTAIR/HER2 correlation was significantly associated with advanced gastric cancers.ConclusionsHOTAIR overexpression represents a biomarker of poor prognosis in gastric cancer, and may confer malignant phenotype to tumor cells. The ceRNA regulatory network involving HOTAIR and the positive interaction between HOTAIR and HER2 may contribute to a better understanding of gastric cancer pathogenesis and facilitate the development of lncRNA-directed diagnostics and therapeutics against this disease.

Long noncoding RNAs (lncRNA) have been implicated in human cancer but their mechanisms of action are mainly undocumented. In this study, we investigated lncRNA alterations that contribute to gastric cancer through an analysis of The Cancer Genome Atlas RNA sequencing data and other publicly available microarray data. Here we report the gastric cancer-associated lncRNA HOXA11-AS as a key regulator of gastric cancer development and progression. Patients with high HOXA11-AS expression had a shorter survival and poorer prognosis. In vitro and in vivo assays of HOXA11-AS alterations revealed a complex integrated phenotype affecting cell growth, migration, invasion, and apoptosis. Strikingly, high-throughput sequencing analysis after HOXA11-AS silencing highlighted alterations in cell proliferation and cell-cell adhesion pathways. Mechanistically, EZH2 along with the histone demethylase LSD1 or DNMT1 were recruited by HOXA11-AS, which functioned as a scaffold. HOXA11-AS also functioned as a molecular sponge for miR-1297, antagonizing its ability to repress EZH2 protein translation. In addition, we found that E2F1 was involved in HOXA11-AS activation in gastric cancer cells. Taken together, our findings support a model in which the EZH2/HOXA11-AS/LSD1 complex and HOXA11-AS/miR-1297/EZH2 cross-talk serve as critical effectors in gastric cancer tumorigenesis and progression, suggesting new therapeutic directions in gastric cancer. Cancer Res; 76(21); 6299-310. ©2016 AACR.

BackgroundLong non-coding RNAs play an important role in tumorigenesis, hence, identification of cancer-associated lncRNAs and investigation of their biological functions and molecular mechanisms are important for understanding the development and progression of cancer. Recently, the downregulation of lncRNA MEG3 has been observed in various human cancers. However, its role in non-small cell lung cancer (NSCLC) is unknown. The aim of this study was to examine the expression pattern of MEG3 in NSCLC and to evaluate its biological role and clinical significance in tumor progression.MethodsExpression of MEG3 was analyzed in 44 NSCLC tissues and 7 NSCLC cell lines by qRT-PCR. Over-expression approaches were used to investigate the biological functions of MEG3 in NSCLC cells. Bisulfite sequencing was used to investigate DNA methylation on MEG3 expression. The effect of MEG3 on proliferation was evaluated by MTT and colony formation assays, and cell apoptosis was evaluated by Hoechst staining and Flow-cytometric analysis. NSCLC cells transfected with pCDNA-MEG3 were injection into nude mice to study the effect of MEG3 on tumorigenesis in vivo . Protein levels of MEG3 targets were determined by western blot analysis. Differences between groups were tested for significance using Student’s t-test (two-tailed).ResultsMEG3 expression was decreased in non-small cell lung cancer (NSCLC) tumor tissues compared with normal tissues, and associated with advanced pathologic stage, and tumor size. Moreover, patients with lower levels of MEG3 expression had a relatively poor prognosis. Overexpression of MEG3 decreased NSCLC cells proliferation and induced apoptosis in vitro and impeded tumorigenesis in vivo. MDM2 and p53 protein levels were affected by MEG3 over-expression in vitro.ConclusionsOur findings indicate that MEG3 is significantly down-regulated in NSCLC tissues that could be affected by DNA methylation, and regulates NSCLC cell proliferation and apoptosis, partially via the activition of p53. Thus, MEG3 may represent a new marker of poor prognosis and is a potential therapeutic target for NSCLC intervention.

Long noncoding RNAs are involved in diseases including cancer. Here, we reported that ANRIL (CDKN2B-AS1), a 3.8-kb long noncoding RNA, recruiting and binding to PRC2, was generally upregulated in human gastric cancer (GC) tissues. In a cohort of 120 GC patients, the higher expression of ANRIL was significantly correlated with a higher TNM stage (P=0.041) and tumor size (P=0.001). Multivariate analyses revealed that ANRIL expression served as an independent predictor for overall survival (P=0.036). Further experiments revealed that ANRIL knockdown significantly repressed the proliferation both in vitro and in vivo. We also showed that E2F1 could induce ANRIL and ANRIL-mediated growth promotion is in part due to epigenetic repression of miR-99a/miR-449a in Trans (controlling the targets—mTOR and CDK6/E2F1 pathway) by binding to PRC2, thus forming a positive feedback loop, continuing to promote GC cell proliferation. To our knowledge, this is the first report showed that the role of ANRIL in the progression of GC and ANRIL could crosstalk with microRNAs in epigenetic level. Our results suggest that ANRIL, as a growth regulator, may serve as a candidate prognostic biomarker and target for new therapies in human gastric cancer.

Recent evidence highlights long noncoding RNAs (lncRNA) as crucial regulators of cancer biology that contribute to essential cancer cell functions such as cell proliferation, apoptosis, and metastasis. In non-small cell lung cancer (NSCLC), several lncRNAs' expressions are misregulated and have been nominated as critical actors in NSCLC tumorigenesis. LncRNA ANRIL was first found to be required for the PRC2 recruitment to and silencing of p15 INK4B , the expression of which is induced by the ATM-E2F1 signaling pathway. Our previous study showed that ANRIL was significantly upregulated in gastric cancer, and it could promote cell proliferation and inhibit cell apoptosis by silencing of miR99a and miR449a transcription. However, its clinical significance and potential role in NSCLC is still not documented. In this study, we reported that ANRIL expression was increased in NSCLC tissues, and its expression level was significantly correlated with tumor-node-metastasis stages and tumor size. Moreover, patients with high levels of ANRIL expression had a relatively poor prognosis. In addition, taking advantage of loss-of-function experiments in NSCLC cells, we found that knockdown of ANRIL expression could impair cell proliferation and induce cell apoptosis both in vitro and vivo. Furthermore, we uncover that ANRIL could not repress p15 expression in PC9 cells, but through silencing of KLF2 and P21 transcription. Thus, we conclusively demonstrate that lncRNA ANRIL plays a key role in NSCLC development by associating its expression with survival in patients with NSCLC, providing novel insights on the function of lncRNA-driven tumorigenesis.

BackgroundThe identification of cancer-associated long non-coding RNAs and the investigation of their molecular and biological functions are important for understanding the molecular biology and progression of cancer. HOTAIR (HOX transcript antisense intergenic RNA) has been implicated in several cancers; however, its role in non-small cell lung cancer (NSCLC) is unknown. The aim of the present study was to examine the expression pattern of HOTAIR in NSCLC and to evaluate its biological role and clinical significance in tumor progression.MethodsExpression of HOTAIR was analyzed in 42 NSCLC tissues and four NSCLC cell lines by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Over-expression and RNA interference (RNAi) approaches were used to investigate the biological functions of HOTAIR. The effect of HOTAIR on proliferation was evaluated by MTT and colony formation assays, and cell migration and invasion were evaluated by transwell assays. Tail vein injection of cells was used to study metastasis in nude mice. Protein levels of HOTAIR targets were determined by western blot analysis. Differences between groups were tested for significance using Student’s t-test (two-tailed).ResultsHOTAIR was highly expressed both in NSCLC samples and cell lines compared with corresponding normal counterparts. HOTAIR upregulation was correlated with NSCLC advanced pathological stage and lymph-node metastasis. Moreover, patients with high levels of HOTAIR expression had a relatively poor prognosis. Inhibition of HOTAIR by RNAi decreased the migration and invasion of NSCLC cells in vitro and impeded cell metastasis in vivo. HOXA5 levels were affected by HOTAIR knockdown or over-expression in vitro.ConclusionsOur findings indicate that HOTAIR is significantly up-regulated in NSCLC tissues, and regulates NSCLC cell invasion and metastasis, partially via the down-regulation of HOXA5. Thus, HOTAIR may represent a new marker of poor prognosis and is a potential therapeutic target for NSCLC intervention.

BackgroundMounting evidence indicates that long noncoding RNAs (lncRNAs) could play a pivotal role in cancer biology. However, the overall biological role and clinical significance of PVT1 in gastric carcinogenesis remains largely unknown.MethodsExpression of PVT1 was analyzed in 80 GC tissues and cell lines by qRT-PCR. The effect of PVT1 on proliferation was evaluated by MTT and colony formation assays, and cell apoptosis was evaluated by Flow-cytometric analysis. GC cells transfected with shPVT1 were injected into nude mice to study the effect of PVT1 on tumorigenesis in vivo. RIP was performed to confirm the interaction between PVT1 and EZH2. ChIP was used to study the promoter region of related genes.ResultsThe higher expression of PVT1 was significantly correlated with deeper invasion depth and advanced TNM stage. Multivariate analyses revealed that PVT1 expression served as an independent predictor for overall survival (p = 0.031). Further experiments demonstrated that PVT1 knockdown significantly inhibited the proliferation both in vitro and in vivo. Importantly, we also showed that PVT1 played a key role in G1 arrest. Moreover, we further confirmed that PVT1 was associated with enhancer of zeste homolog 2 (EZH2) and that this association was required for the repression of p15 and p16. To our knowledge, this is the first report showed that the role and the mechanism of PVT1 in the progression of gastric cancer.ConclusionsTogether, these results suggest that lncRNA PVT1 may serve as a candidate prognostic biomarker and target for new therapies in human gastric cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0355-8) contains supplementary material, which is available to authorized users.