Circular RNA circ-TNRC6B inhibits the proliferation and invasion of esophageal squamous cell carcinoma cells by regulating the miR-452-5p/DAG1 axis.

Previous studies have uncovered the key role of circular RNAs (circRNAs) in various diseases, including cancer. However, the growth-inhibitory effects of circRNAs on esophageal squamous cell carcinoma (ESCC) have not been completely elucidated. This study characterized a newly identified circRNA derived from exons 9-13 of TNRC6B (named circ-TNRC6B). The expression of circ-TNRC6B in ESCC tissues was markedly downregulated when compared to that in non-tumor tissues. In 53 ESCC cases, circ-TNRC6B expression was negatively correlated with the T stage. Multivariate Cox regression analysis showed that circ-TNRC6B upregulation was an independent protective factor for ESCC patients' prognosis. Overexpression and knockdown functional experiments demonstrated that circ-TNRC6B inhibited ESCC cell proliferation, migration, and invasion. RNA immunoprecipitation and dual-luciferase reporter assays demonstrated that circ-TNRC6B sponges oncogenic miR-452-5p to upregulate the expression and activity of DAG1. Treatment with miR-452-5p inhibitor partially reversed the circ-TNRC6B-induced changes in the biological behavior of ESCC cells. These findings demonstrated that circ-TNRC6B exerts a tumor-suppressing effect in ESCC through the miR-452-5p/DAG1 axis. Thus, circ-TNRC6B is a potential prognostic biomarker for the clinical management of ESCC.

Circular RNA circCCDC85A inhibits breast cancer progression via acting as a miR-550a-5p sponge to enhance MOB1A expression.

BACKGROUND: A growing body of evidence indicates that abnormal expression of circular RNAs (circRNAs) plays a crucial role by acting as molecular sponges of microRNAs (miRNAs) in various diseases, including cancer. In this study, we explored whether circCCDC85A could function as a miR-550a-5p sponge and influence breast cancer progression. METHODS: We detected the expression of circCCDC85A in breast cancer tissues and cells using fluorescence in situ hybridization (FISH) and quantitative reverse transcription polymerase chain reaction (qRT-PCR). CCK-8 and colony formation assay were used to detect the proliferative ability of breast cancer cells. Wound healing assay and transwell migration and invasion assays were used to detect the migrative and invasive abilities of breast cancer cells. We also examined the interactions between circCCDC85A and miR-550a-5p using FISH, RNA-binding protein immunoprecipitation (RIP), and luciferase reporter assay. Moreover, we performed luciferase reporter assay, qRT-PCR, and Western blot to confirm the direct targeting of miR-550a-5p to MOB1A. RESULTS: The expression of circCCDC85A in breast cancer tissues was obviously lower than that in normal breast tissues. Over-expression of circCCDC85A substantially inhibited the proliferative, migrative, and invasive ability of breast cancer cells, while knocking down of circCCDC85A enhanced the aforementioned properties of breast cancer cells. Moreover, enforced expression of circCCDC85A inhibits the oncogenic activity of miR-550a-5p and increases the expression of MOB1A targeted by miR-550a-5p. Further molecular mechanism research showed that circCCDC85A may act as a molecular sponge for miR-550a-5p, thus restoring miR-550a-5p-mediated targeting repression of tumor suppressor MOB1A in breast cancer cells. CONCLUSION: Our findings provide novel evidence that circCCDC85A inhibits the progression of breast cancer by functioning as a molecular sponge of miR-550a-5p to enhance MOB1A expression.