Identification and function of circular RNA hsa_circ_0071106: A novel biomarker for differentiation degree of esophageal squamous cell carcinoma

Abstract

BackgroundEsophageal squamous cell carcinoma (ESCC) has a high degree of malignancy, and there is currently no effective treatment. Circular RNA is a novel endogenous noncoding RNA with a stable loop structure. Several theories have been proposed regarding its biogenesis and usefulness as a biomarker in various cancers. Here we explore the predictive value and potential functions of a candidate circRNA (hsa_circ_0071106) in ESCC. MethodsThe altered expression of hsa_circ_0071106 was validated in clinical tissue samples from 64 patients with ESCC. The correlation between the clinical characteristics of these patients and the expression of hsa_circ_0071106 was analyzed by the chi-square test. The receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were used to evaluate the diagnostic value of hsa_circ_0071106. The human esophageal carcinoma cell lines ECA109 and ECA9706 and the normal human esophageal epithelial cell line (HET-1A) were applied for functional analysis of hsa_circ_0071106. qRT-PCR, sanger sequencing, agarose gel electrophoresis, RNase R digestion assay, Actinomycin D inhibition assay, nucleoplasm separation assay, and FISH assays were utilized to verify the circular characteristics and subcellular localization of hsa_circ_0071106. SiRNA and circRNA interference lentivirus was constructed to inhibit the expression of hsa_circ_0071106 in the ECA109 and ECA9706 cell lines. We used the EdU assay, Transwell assay, and flow cytometry to detect changes in cell proliferation, invasion, migration, and apoptosis. ResultsWe identified that hsa_circ_0071106 showed significantly decreased expression levels in ESCC cells (P < 0.001) and tissue samples (P < 0.001). The correlation analysis of clinicopathological features and gene expression revealed that low expression of hsa_circ_0071106 was related to poor differentiation grade (P < 0.05). ROC curves indicated that hsa_circ_0071106 might have a diagnostic value for ESCC (AUC = 0.826, 95% CI: 0.748–0.904) and a predictive value for a high degree of histological differentiation (AUC = 0.730, 95% CI: 0.607–0.854). Hsa_circ_0071106 has a stable circular structure and was primarily localized in the cytoplasm. A transient knockdown of hsa_circ_0071106 by siRNA promotes proliferation, migration, and invasion and inhibits apoptosis of ESCC cells. A steady knockdown of hsa_circ_0071106 by a lentivirus knockout vector significantly promoted cell migration and invasion in ECA109 and ECA9706 cell lines. ConclusionHsa_circ_0071106 was a downregulated circRNA related to ESCC and promoted ESCC progression by regulating cell migration and invasion. These findings suggest that hsa_circ_0071106 could be a promising diagnostic biomarker and potential therapeutic target and might predict ESCC’s histological differentiation degree.