Aberrant methylation-mediated silencing of lncRNA CTC-276P9.1 is associated with malignant progression of esophageal squamous cell carcinoma

Mutual interaction of lncRNAs and epigenetics: focusing on cancer

Long noncoding RNAs are characterized as noncoding transcripts longer than 200 nucleotides in response to a variety of functions within the cells. They are involved in almost all cellular mechanisms so as epigenetics. Given that epigenetics is an important phenomenon, which participates in the biology of complex diseases, many valuable studies have been performed to demonstrate the control status of lncRNAs and epigenetics. DNA methylation and histone modifications as epigenetic mechanisms can regulate the expression of lncRNAs by affecting their coding genes. Reciprocally, the three-dimensional structure of lncRNAs could mechanistically control the activity of epigenetic-related enzymes. Dysregulation in the mutual interaction between epigenetics and lncRNAs is one of the hallmarks of cancer. These mechanisms are either directly or indirectly involved in various cancer properties such as proliferation, apoptosis, invasion, and metastasis. For instance, lncRNA HOTAIR plays a role in regulating the expression of many genes by interacting with epigenetic factors such as DNA methyltransferases and EZH2, and thus plays a role in the initiation and progression of various cancers. Conversely, the expression of this lncRNA is also controlled by epigenetic factors. Therefore, focusing on this reciprocated interaction can apply to cancer management and the identification of prognostic, diagnostic, and druggable targets. In the current review, we discuss the reciprocal relationship between lncRNAs and epigenetic mechanisms to promote or prevent cancer progression and find new potent biomarkers and targets for cancer diagnosis and therapy.

Ferroptosis-Related lncRNA Signature Correlates with the Prognosis, Tumor Microenvironment, and Therapeutic Sensitivity of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most prevalent form of esophageal cancer in China and is closely associated with malignant biological characteristics and poor survival. Ferroptosis is a newly discovered iron-dependent mode of cell death that plays an important role in the biological behavior of ESCC cells. The clinical significance of ferroptosis-related long noncoding RNAs (FRLs) in ESCC remains unknown and warrants further research. The current study obtained RNA sequencing profiles and corresponding clinical data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, and FRLs were obtained through coexpression analysis. Consensus clustering was employed to divide the subjects into clusters, and immune-associated pathways were identified by functional analysis. The current study observed significant differences in the enrichment scores of immune cells among different clusters. Patients from TCGA-ESCC database were designated as the training cohort. A ten-FRL prediction signature was established using the least absolute shrinkage and selection operator Cox regression model and validated using the GEO cohort and our own independent validation database. Real-time quantitative polymerase chain reaction was used to verify the expression of the ten FRLs, and the ssGSEA analysis was employed to evaluate their function. In addition, the IMvigor database was used to assess the predictive value of the signature in terms of immunotherapeutic responses. Multivariate Cox and stratification analyses revealed that the ten-FRL signature was an independent predictor of the overall survival (OS). Patients with ESCC in the high-risk group displayed worse survival, a characteristic tumor immune microenvironment, and low immunotherapeutic benefits compared to those in the low-risk group. Collectively, the risk model established in this study could serve as a promising predictor of prognosis and immunotherapeutic response in patients with ESCC.

Downregulation of LINC00886 facilitates epithelial-mesenchymal transition through SIRT7/ELF3/miR-144 pathway in esophageal squamous cell carcinoma

LINC00886 has been reported to be down-regulated in laryngeal squamous cell carcinoma, and aberrant DNA methylation status of it has been screened in several tumor types. However, the roles of LINC00886 in esophageal squamous cell carcinoma (ESCC) remained unclarified. The present study was to investigate the expression level, epigenetic inactivation mechanisms, and functions of LINC00886 in ESCC tumorigenesis. Frequent down-regulation of LINC00886 was verified in esophageal cancer cells and ESCC tissues. There are CpG islands spanning the promoter and exon 1 regions of LINC00886 gene, and DNA hypermethylation of proximal promoter led to transcriptional inhibition of LINC00886, moreover, histone modification also played certain roles in LINC00886 transcription. LINC00886 functioned as a tumor suppressor by inhibiting proliferation, migration, and invasion of esophageal cancer cells. LINC00886 was down-regulated following TGF-β1 treatment in esophageal cancer cells and participated in epithelial-mesenchymal transition (EMT) process by regulating EMT-related genes, especially ZEB1 and ZEB2. ELF3 was proved to be one of the downstream target genes of LINC00886. LINC00886 may interact with and recruit SIRT7 to decrease acetylation level of H3K18 on the promoter region of ELF3 to inhibit its expression. Furthermore, ELF3 may promote EMT process via promoting ZEB1 and ZEB2 expression through binding to the promoter region of miR-144 to suppress miR-144-3p transcriptional activity in ESCC. These data suggest that LINC00886 may act as a tumor suppressor gene in ESCC and its down-regulation through epigenetic mechanisms promotes EMT process via SIRT7/ELF3/miR-144 pathway in ESCC. Thus, LINC00886 may be a potential therapeutic target for ESCC treatment.

A Pleiotropic Role of Long Non-Coding RNAs in the Modulation of Wnt/β-Catenin and PI3K/Akt/mTOR Signaling Pathways in Esophageal Squamous Cell Carcinoma: Implication in Chemotherapeutic Drug Response

Despite the availability of modern techniques for the treatment of esophageal squamous cell carcinoma (ESCC), tumor recurrence and metastasis are significant challenges in clinical management. Thus, ESCC possesses a poor prognosis and low five-year overall survival rate. Notably, the origin and recurrence of the cancer phenotype are under the control of complex cancer-related signaling pathways. In this review, we provide comprehensive knowledge about long non-coding RNAs (lncRNAs) related to Wnt/β-catenin and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway in ESCC and its implications in hindering the efficacy of chemotherapeutic drugs. We observed that a pool of lncRNAs, such as HERES, TUG1, and UCA1, associated with ESCC, directly or indirectly targets various molecules of the Wnt/β-catenin pathway and facilitates the manifestation of multiple cancer phenotypes, including proliferation, metastasis, relapse, and resistance to anticancer treatment. Additionally, several lncRNAs, such as HCP5 and PTCSC1, modulate PI3K/Akt/mTOR pathways during the ESCC pathogenesis. Furthermore, a few lncRNAs, such as AFAP1-AS1 and LINC01014, block the efficiency of chemotherapeutic drugs, including cisplatin, 5-fluorouracil, paclitaxel, and gefitinib, used for ESCC treatment. Therefore, this review may help in designing a better therapeutic strategy for ESCC patients.

Long Non-Coding RNA in Esophageal Cancer: A Review of Research Progress

In recent years, there has been significant progress in the diagnosis and treatment of esophageal cancer. However, owing to the lack of early diagnosis strategies and treatment targets, the prognosis of patients with esophageal cancer remains unsatisfactory. There is an urgent need to identify novel biomarkers and treatment targets for esophageal cancer. With the development of genomics, long-chain non-coding RNAs (LncRNAs), which were once considered transcriptional “noise,” are being identified and characterized rapidly in large numbers. Recent research shows that LncRNAs are closely related to a series of steps in tumor development and play an important regulatory role in DNA replication, transcription, and post-transcriptional regulation. The abnormal expression of LncRNAs leads to tumor cell proliferation, migration, invasion, and treatment resistance. This review focuses on the latest progress in research on the abnormal expression and functional mechanisms of LncRNAs in esophageal cancer. Further, it discusses the potential applications of these findings towards achieving an early diagnosis, improving treatment efficacy, and evaluating the prognosis of esophageal cancer.

LncRNA DDX11 antisense RNA 1 promotes EMT process of esophageal squamous cell carcinoma by sponging miR-30d-5p to regulate SNAI1/ZEB2 expression and Wnt/β-catenin pathway

LncRNA DDX11 antisense RNA 1 (DDX11-AS1) is recognized as having an imperative oncogenic role in different types of human cancer. Nevertheless, the functions, as well as the basic mechanisms of DDX11-AS1 in the EMT process of esophageal squamous cell carcinoma (ESCC), are yet to be clarified. In this research, high DDX11-AS1 expression was detected in ESCC cells as well as tissues and was linked to the poor prognosis of patients with ESCC. DDX11-AS1 promoted cell proliferation, migration, invasion ability and epithelial mesenchymal transition (EMT) process in vitro. Mechanistic analysis depicted that DDX11-AS1 may function as a ceRNA through sponging miR-30d-5p to upregulate the expression of SNAI1 and ZEB2. Meanwhile, overexpression of DDX11-AS1 might cause the activation of the Wnt/β-catenin signaling pathway via targeting miR-30d-5p. On the whole, the findings of this research illustrate that DDX11-AS1 may act as an EMT-related lncRNA to advance ESCC progression through sponging miR-30d-5p to regulate SNAI1/ZEB2 expression and activate the Wnt/β-catenin pathway, which indicates that it might serve as a probable therapeutic target for ESCC.

Role of hypermethylated-lncRNAs in the prognosis of bladder cancer patients

OBJECTIVE

To explore the hypermethylated long non-coding (lnc)RNAs involved in bladder carcinogenesis and prognosis.

METHODS

Reduced representation bisulfite sequencing and RNA sequencing were performed on five paired tumor and adjacent normal tissue samples from bladder cancer patients. The differentially methylated regions around transcription start sites and differentially expressed genes, including lncRNAs, were analyzed. Correlations between DNA methylation modifications and the expression of lncRNAs were examined. Survival analysis was surveyed on the GEPIA web server.

RESULTS

We identified 19,560 hypomethylated and 68,781 hypermethylated differentially methylated regions around transcription start sites in bladder cancer tissues. In total, 2321 differentially expressed genes were found in bladder tumors, among which, 367 were upregulated and 1954 were downregulated. There were 141 downregulated genes involving eight lncRNAs that were consistently hypermethylated, while 24 upregulated genes were consistently hypomethylated. Survival analysis demonstrated that hypermethylation of lncRNAs LINC00683 and MSC-AS1 were associated with poor overall survival in bladder cancer patients.

CONCLUSION

Some lncRNAs are controlled by DNA methylation in bladder cancer and they might be important factors in bladder carcinogenesis. Hypermethylated lncRNAs including LINC00683 and MSC-AS1 have the potential to be prognostic biomarkers for bladder cancer.

SNHG5 inhibits the progression of EMT through the ubiquitin-degradation of MTA2 in oesophageal cancer

A substantial fraction of transcripts are known as long noncoding RNAs (lncRNAs), and these transcripts play pivotal roles in the development of cancer. However, little information has been published regarding the functions of lncRNAs in oesophageal squamous cell carcinoma (ESCC) and the underlying mechanisms. In our previous studies, we demonstrated that small nucleolar RNA host gene 5 (SNHG5), a known lncRNA, is dysregulated in gastric cancer (GC). In this study, we explored the expression and function of SNHG5 in development of ESCC. SNHG5 was found to be downregulated in human ESCC tissues and cell lines, and this downregulation was associated with cancer progression, clinical outcomes and survival rates of ESCC patients. Furthermore, we also found that overexpression of SNHG5 significantly inhibited the proliferation, migration and invasion of ESCC cells in vivo and in vitro. Notably, we found that metastasis-associated protein 2 (MTA2) was pulled down by SNHG5 in ESCC cells using RNA pulldown assay. We also found that SNHG5 reversed the epithelial-mesenchymal transition by interacting with MTA2. In addition, overexpression of SNHG5 downregulated the transcription of MTA2 and caused its ubiquitin-mediated degradation. Thus, overexpression of MTA2 partially abrogated the effect of SNHG5 in ESCC cell lines. Furthermore, we found that MTA2 mRNA expression was significantly elevated in ESCC specimens, and a negative correlation between SNHG5 and MTA2 expression was detected. Overall, this study demonstrated, for the first time, that SNHG5-regulated MTA2 functions as an important player in the progression of ESCC and provide a new potential therapeutic strategy for ESCC.

Evaluation of C5orf66-AS1 as a Potential Biomarker for Predicting Early Gastric Cancer and Its Role in Gastric Carcinogenesis

Background

Long non-coding RNAs (lncRNAs) participate in a series of pathological processes in tumorigenesis. Reports show that C5orf66-AS1, an antisense lncRNA, is expressed in various tumors. However, the role of C5orf66-AS1 in gastric cancer (GC) has not been fully clarified. The study focused on the expression patterns and serum level of C5orf66-AS1 in GC to explore its potential application in GC screening and diagnosis. The effects of C5orf66-AS1 on GC cells were also analyzed.

Methods

Tissue and serum samples were used for RNA isolation. Expression levels of C5orf66-AS1 in GC tissues, serum, and cell lines were detected using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). CCK-8, transwell, and wound healing assays were performed to determine the effects of C5orf66-AS1 on GC cell behavior.

Results

C5orf66-AS1 expression was downregulated in GC cells compared to that in adjacent normal tissues. Serum C5orf66-AS1 levels were significantly lower in GC patients than in superficial gastritis (GS) and atrophic gastritis (GA) patients. Low serum expression of C5orf66-AS1 was associated with an increased risk of gastric dysplasia (GD) and GC. Receiver operating characteristic curve results showed that the area under curve (AUC) for GC was 0.688, with a sensitivity and specificity of 77.5% and 53.6%, respectively. For the GD + early gastric cancer (ECG) group, the AUC was 0.789, with a sensitivity and specificity of 85.15% and 62.86%, respectively. Correlation analyses of clinicopathological parameters showed that serum C5orf66-AS1 was predominantly associated with Lauren type, TNM stages, pTNM stages, and vessel tumor emboli. Additionally, in vitro overexpression of C5orf66-AS1 in AGS cells inhibited cell proliferation, migration, and invasion.

Conclusion

Decreased expression levels of serum C5orf66-AS1 can be utilized for diagnosis of GC, especially for early diagnosis. The low level of serum C5orf66-AS1 indicated poor biological behavior of tumors in GC patients. In addition, C5orf66-AS1 can inhibit GC cell proliferation, migration, and invasion.

Aberrant DNA hypermethylation-silenced LINC00886 gene accelerates malignant progression of laryngeal carcinoma

BACKGROUND

Long noncoding RNAs (lncRNAs) play crucial role in formation and progression of tumors. DNA methylation has become increasingly recognized as a frequent event of epigenetic alterations and one of the primary mechanisms of gene inactivation. The research aims to investigate the biofunction of a novel lncRNA in LSCC.

METHODS

qRT-PCR, BGS, and MSP methods were employed to measure the relative expression level and methylation status of LINC00886. Additionally, we examined the effects of LINC00886 on cells proliferation and invasion using LINC00886 over-expression. Nude mouse xenograft models were conducted to assess LINC00886 effects on LSCC growth in vivo. High-throughput sequencing technology and Western blot assay were carried out to have an in-depth study of the downstream target genes and signaling pathways in which LINC00886 may participate.

RESULTS

The remarkable downregulation of LINC00886 was observed in tumor tissues and laryngeal cancer cell lines. The significant decrease of LINC00886 was correlated with pathological grade in LSCC tissues. The expression level of LINC00886 in laryngeal cancer cell lines was significantly reversed by 5-Aza-dC. The occurrence of aberrant methylation events in the LINC00886 TSS was more responsible for the down-expression of LINC00886. Over-expression of LINC00886 dramatically mitigated cell proliferation, migration, and invasion in vitro as well as suppressed tumor growth in vivo. LINC00886 may be associated with VEGFA/PI3K/AKT signaling pathways and epithelial-mesenchymal transition (EMT) process.

CONCLUSIONS

We provide the first evidence of the involvement of LINC00886 in laryngeal carcinoma, which was downregulated due to methylation of the promoter region and served as tumor suppressor genes. LINC00886 is expected to become a novel biomarker in laryngeal carcinoma.

lncRNA TMEM51-AS1 and RUSC1-AS1 function as ceRNAs for induction of laryngeal squamous cell carcinoma and prediction of prognosis

BACKGROUND

Long non-coding RNAs (lncRNAs) can function as competing endogenous RNAs (ceRNAs) to interact with miRNAs to regulate target genes and promote cancer initiation and progression. The expression of lncRNAs and miRNAs can be epigenetically regulated. The goal of this study was to construct an lncRNA-miRNA-mRNA ceRNA network in laryngeal squamous cell carcinoma (LSCC) and reveal their methylation patterns, which was not investigated previously.

METHODS

Microarray datasets available from the Gene Expression Omnibus database were used to identify differentially expressed lncRNAs (DELs), miRNAs (DEMs), and genes (DEGs) between LSCC and controls, which were then overlapped with differentially methylated regions (DMRs). The ceRNA network was established by screening the interaction relationships between miRNAs and lncRNAs/mRNAs by corresponding databases. TCGA database was used to identify prognostic biomarkers.

RESULTS

Five DELs (downregulated: TMEM51-AS1, SND1-IT1; upregulated: HCP5, RUSC1-AS1, LINC00324) and no DEMs were overlapped with the DMRs, but only a negative relationship occurred in the expression and methylation level of TMEM51-AS1. Five DELs could interact with 11 DEMs to regulate 242 DEGs, which was used to construct the ceRNA network, including TMEM51-AS1-miR-106b-SNX21/ TRAPPC10, LINC00324/RUSC1-AS1-miR-16-SPRY4/MICAL2/ SLC39A14, RUSC1-AS1-miR-10-SCG5 and RUSC1-AS1-miR-7-ZFP1 ceRNAs axes. Univariate Cox regression analysis showed RUSC1-AS1 and SNX21 were associated with overall survival (OS); LINC00324, miR-7 and ZFP1 correlated with recurrence-free survival (RFS); miR-16, miR-10, SCG5, SPRY4, MICAL2 and SLC39A14 were both OS and RFS-related. Furthermore, TRAPPC10 and SLC39A14 were identified as independent OS prognostic factors by multivariate Cox regression analysis.

CONCLUSION

DNA methylation-mediated TMEM51-AS1 and non-methylation-mediated RUSC1-AS1 may function as ceRNAs for induction of LSCC. They and their ceRNA axis genes (particularly TMEM51-AS1-miR-106b-TRAPPC10; RUSC1-AS1-miR-16-SLC39A14) may be potentially important prognostic biomarkers for LSCC.

Involvement of noncoding RNAs in epigenetic modifications of esophageal cancer

Esophageal cancer (EC) is a serious digestive malignancy and is a leading cause of cancer-related mortality. Apart from genetic mutations, many epigenetic alterations including DNA methylation and histone modifications associated with chromatin remodeling have been identified in the regulation of gene expression in EC. Recently, noncoding RNAs, and mainly lncRNAs and miRNAs, have been revealed to be involved in the epigenetic regulation of EC. In this review, we focus on describing new insights on epigenetic processes associated with noncoding RNAs, which have been characterized to be responsible for the development and progression of EC.

The long non-coding RNA Linc-GALH promotes hepatocellular carcinoma metastasis via epigenetically regulating Gankyrin

Hepatocellular carcinoma (HCC) is the most prevalent subtype of liver cancer, and it is characterized by high rate of metastasis and recurrence. Recent studies have boosted our understanding that Gankyrin contributes to both of these pathological properties, but the mechanisms underlying its aberrant regulation are poorly understood. Recently, many long noncoding RNAs (lncRNAs) have been reported to be involved in regulating the expression of oncogenes and anti-oncogenes through various mechanisms. Here, using transcriptome microarray analysis, we identified a long intergenic noncoding RNA termed Linc-GALH that was highly expressed and concordance with Gankyrin expression in HCC. In addition, we revealed that Linc-GALH was an independent unfavorable prognostic indicator for HCC, followed functional experiments showed that Linc-GALH promoted HCC cells migration and invasion in vitro, and enhanced lung metastasis ability of HCC cells in vivo. Mechanistically, we found that Linc-GALH could regulate the expression of Gankyrin through controlling the methylation status of Gankyrin by adjusting the ubiquitination status of DNMT1 in HCC. Collectively, our results demonstrated the role and functional mechanism of Linc-GALH in HCC, and indicated that Linc-GALH may act as a prognostic biomarker and potential therapeutic target for HCC.

The downregulated long noncoding RNA DHRS4-AS1 is protumoral and associated with the prognosis of clear cell renal cell carcinoma

BACKGROUND

Long noncoding RNAs (lncRNAs) have been identified as important factors in cancer biology and are deregulated in many cancers. The present study aimed to determine the expression and roles of lncRNA DHRS4-AS1 in the progression of clear cell renal cell carcinoma (ccRCC).

METHODS AND RESULTS

Using high-throughput RNA-sequencing data of ccRCC tumors from the Cancer Genome Atlas project, we identified lncRNA DHRS4-AS1 as significantly associated with ccRCC patients' overall survival. We confirmed the downregulation of DHRS4-AS1 in ccRCC by assessing its expression levels in a cohort of 52 tumor and paired non-tumor samples. In addition, we found that low DHRS4-AS1 expression was significantly associated with a high tumor node metastasis stage, lymph node metastasis, advanced pathological grade and poor prognosis. Furthermore, DHRS4-AS1 overexpression inhibited the progression of cell cycles of ccRCC in vitro. These data indicate that DHRS4-AS1 functions by preventing the proliferation and invasion, inhibiting the cell cycle progression and promoting the apoptosis of ccRCC cells.

CONCLUSION

Taken together, our findings identify the role of DHRS4-AS1 as a tumor inhibitor in ccRCC for the first time, demonstrating that DHRS4-AS1 is a potential prognostic biomarker that could potentially be applied in ccRCC therapy.

The Nefarious Nexus of Noncoding RNAs in Cancer

The past decade has witnessed enormous progress, and has seen the noncoding RNAs (ncRNAs) turn from the so-called dark matter RNA to critical functional molecules, influencing most physiological processes in development and disease contexts. Many ncRNAs interact with each other and are part of networks that influence the cell transcriptome and proteome and consequently the outcome of biological processes. The regulatory circuits controlled by ncRNAs have become increasingly more relevant in cancer. Further understanding of these complex network interactions and how ncRNAs are regulated, is paving the way for the identification of better therapeutic strategies in cancer.

Long non-coding RNA TUG1 protects renal tubular epithelial cells against injury induced by lipopolysaccharide via regulating microRNA-223

BACKGROUND

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE). Long non-coding RNA taurine upregulated gene 1 (lncRNA TUG1) exerted critical regulatory effects on inhibiting cell injury and inflammation. However, its role in LN is still unclear.

METHODS

HK-2 cells were treated with lipopolysaccharide (LPS) to simulate cell inflammatory injury. Cell viability and apoptosis, as well as pro-inflammatory factors expression were measured, respectively. Then, HK-2 cells were transfected with pEX-TUG1 or sh-TUG1 to explore the effects of TUG1 on LPS-induced cell injury. Potential binding effects between TUG1 and microRNA-223 (miR-223), as well as between miR-223 and Sirtuin 1 (Sirt1) were verified. miR-223 mimic or miR-223 inhibitor was transfected to assess the effects of miR-223 on cell injury. Finally, the roles of Sirt1 in LPS-induced HK-2 cell injury and activation of phosphatidylinositol 3-kinase/protein kinase 3 (PI3K/AKT) and nuclear factor kappa B (NF-κB) pathways were explored.

RESULTS

LPS administration inhibited HK-2 cell viability and proliferation, increased expression of pro-inflammatory factors, and promoted cell apoptosis. TUG1 overexpression protected HK-2 cells against LPS-induced injury via negatively regulating miR-223 expression. TUG1 suppression had opposite effects. Sirt1 was a direct target gene of miR-223 in HK-2 cells, which participated in the effects of miR-223 on HK-2 cells and was related with the activation of PI3K/AKT and NF-κB pathways.

CONCLUSION

TUG1 protected HK-2 cells against LPS-induced inflammatory injury by regulating miR-223 and Sirt1 expression, and then activating PI3K/AKT and inactivating NF-κB pathways. TUG1 might be a potential therapeutic target for LN treatment.