Genome-wide analysis of long non-coding RNAs in esophageal squamous cell carcinoma reveals their potential role in invasion and metastasis

Circular RNA 0014715 Facilitates Cell Proliferation and Inhibits Apoptosis in Esophageal Squamous Cell Carcinoma

Background

Circular RNAs (circRNAs) have recently been verified to have multiple biological functions and participate in diverse biological processes in different malignant tumors, including esophageal squamous cell carcinoma (ESCC). Nonetheless, the function of circular RNA 0014715 (hsa_circ_0014715, circ_0014715) in ESCC has not been described.

Materials and Methods

We investigated clinical data from sixty-seven patients undergoing surgery for esophageal cancer. The clinical data were collected. And we analyzed the correlation between the clinical characteristics of these patients and the expression of circ_0014715. Besides, we explored the expression of circ_0014715 in ESCC cell lines. We used cell counting kit-8, colony formation, transwell assay, and flow cytometry to detect changes in cell proliferation, migration, apoptosis, and cell cycle progression.

Results

We found that circ_0014715 was highly expressed in esophageal squamous cell carcinoma tissues and cell lines. The correlation analysis of clinicopathological features and gene expression revealed that high expression of circ_0014715 was related to nerve invasion, vascular invasion, more advanced tumor-node-metastasis (TNM) stage and poor differentiation grade. Receiver operating characteristic (ROC) curves revealed that circ_0014715 might have diagnostic value for ESCC. Experiments with cultured cells showed that knockdown of circ_0014715 significantly restrained cell proliferation, migration, invasion, wound healing and accelerated cell apoptosis. And cell cycle arrest at G2 phase was observed via flow cytometry. Overexpression of circ_0014715 caused the opposite effects. Collectively, these studies show that circ_0014715 is closely connected with the pathogenesis and development of ESCC. The excess expression of circ_0014715 may have promoting effects on the progression of esophageal cell carcinoma.

Conclusion

Our finding revealed that circ_0014715 promoted tumor growth and cell proliferation. All of these suggest that targeting circ_0014715 has potential therapeutic value in the treatment of ESCC.

Involvement of long non-coding RNAs in the progression of esophageal cancer

Esophageal cancer (EC) is one of the most common malignant tumors of the digestive system with high incidence and mortality rate worldwide. Therefore, exploring the pathogenesis of EC and searching for new targeted therapies are the current research hotspot for EC treatment. Long non‐coding RNAs (lncRNAs) are endogenous RNAs with more than 200 nucleotides, but without protein‐coding function. In recent years, lncRNAs have gradually become the focuses in the field of non‐coding RNA. Some lncRNAs have been proved to be closely related to the pathogenesis of EC. Many lncRNAs are abnormally expressed in EC and participate in many biological processes including cell proliferation, apoptosis, and metastasis by inhibiting or promoting target gene expression. LncRNAs can also regulate the progression of EC through epithelial‐mesenchymal transformation (EMT), which is closely related to the occurrence, development, and prognosis of EC. In this article, we review and discuss the involvement of lncRNAs in the progression of EC.

The prognostic value of a seven-lncRNA signature in patients with esophageal squamous cell carcinoma: a lncRNA expression analysis

Background

Long non-coding RNAs (lncRNAs) have been reported to be prognostic biomarkers in many types of cancer. We aimed to identify a lncRNA signature that can predict the prognosis in patients with esophageal squamous cell carcinoma (ESCC).

Methods

Using a custom microarray, we retrospectively analyzed lncRNA expression profiles in 141 samples of ESCC and 81 paired non-cancer specimens from Sun Yat-Sen University Cancer Center (Guangzhou, China), which were used as a training cohort to identify a signature associated with clinical outcomes. Then we conducted quantitative RT-PCR in another 103 samples of ESCC from the same cancer center as an independent cohort to verify the signature.

Results

Microarray analysis showed that there were 338 lncRNAs significantly differentially expressed between ESCC and non-cancer esophagus tissues in the training cohort. From these differentially expressed lncRNAs, we found 16 lncRNAs associated with overall survival (OS) of ESCC patients using Cox regression analysis. Then a 7-lncRNA signature for predicting survival was identified from the 16 lncRNAs, which classified ESCC patients into high-risk and low-risk groups. Patients with high-risk have shorter OS (HR: 3.555, 95% CI 2.195–5.757, p < 0.001) and disease-free survival (DFS) (HR: 2.537, 95% CI 1.646–3.909, p < 0.001) when compared with patients with low-risk in the training cohort. In the independent cohort, the 7 lncRNAs were detected by qRT-PCR and used to compute risk score for the patients. The result indicates that patients with high risk also have significantly worse OS (HR = 2.662, 95% CI 1.588–4.464, p < 0.001) and DFS (HR 2.389, 95% CI 1.447–3.946, p < 0.001). The univariate and multivariate Cox regression analyses indicate that the signature is an independent factor for predicting survival of patients with ESCC. Combination of the signature and TNM staging was more powerful in predicting OS than TNM staging alone in both the training (AUC: 0.772 vs 0.681, p = 0.002) and independent cohorts (AUC: 0.772 vs 0.660, p = 0.003).

Conclusions

The 7-lncRNA signature is a potential prognostic biomarker in patients with ESCC and may help in treatment decision when combined with the TNM staging system.

Integrated analysis highlights multiple long non‑coding RNAs and their potential roles in the progression of human esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a prevalent aggressive malignant tumor with poor prognosis. Investigations into the molecular changes that occur as a result of the disease, as well as identification of novel biomarkers for its diagnosis and prognosis, are urgently required. Long non‑coding RNAs (lncRNAs) have been reported to play a critical role in tumor progression. The present study performed data mining analyses for ESCC via an integrated study of accumulated datasets and identification of the differentially expressed lncRNAs from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. The identified intersection of differentially expressed genes (lncRNAs, miRNAs and mRNAs) in ESCC tissues between the GEO and TCGA datasets was investigated. Based on these intersected lncRNAs, the present study constructed a competitive endogenous RNA (ceRNA) network of lncRNAs in ESCC. A total of 81 intersection lncRNAs were identified; 67 of these were included in the ceRNA network. Functional analyses revealed that these 67 key lncRNAs primarily dominated cellular biological processes. The present study then analyzed the associations between the expression levels of these 67 key lncRNAs and the clinicopathological characteristics of the ESCC patients, as well as their survival time using TCGA. The results revealed that 31 of these lncRNAs were associated with tumor grade, tumor‑node‑metastasis (TNM) stage and lymphatic metastasis status (P<0.05). In addition, 15 key lncRNAs were demonstrated to be associated with survival time (P<0.05). Finally, 5 key lncRNAs were selected for validation of their expression levels in 30 patients newly diagnosed with ESCC via reverse transcription‑quantitative PCR (RT‑qPCR). The results suggested that the fold changes in the trends of up‑ and downregulation between GEO, TCGA and RT‑qPCR were consistent. In addition, it was also demonstrated that a select few of these 5 key lncRNAs were significantly associated with TNM stage and lymph node metastasis (P<0.05). The results of the clinically relevant analysis and the aforementioned bioinformatics were similar, hence proving that the bioinformatics analysis used in the present study is credible. Overall, the results from the present study may provide further insight into the functional characteristics of lncRNAs in ESCC through bioinformatics integrative analysis of the GEO and TCGA datasets, and reveal potential diagnostic and prognostic biomarkers for ESCC.