Circular RNA hsa_circ_0061825 (circ-TFF1) contributes to breast cancer progression through targeting miR-326/TFF1 signalling.

OBJECTIVES: Circular RNAs (circRNAs) are RNA transcripts that belong to non-coding RNAs (ncRNAs), whose implication in human cancers has been recently demonstrated. However, the specific role of multiple circRNAs in breast cancer remains unidentified. MATERIALS AND METHODS: Microarray analysis and bioinformatics analysis were applied to select circRNA and miRNA, respectively. The loop structure of circ-TFF1 was confirmed using RNase R treatment, divergent primer PCR and Sanger sequencing. qRT-PCR and Western blot were employed for gene expressions. In vitro and in vivo experiments were conducted to assess the function of circ-TFF1 in biological processes in breast cancer cells. FISH and subcellular separation indicated circ-TFF1 cellular distribution. Luciferase reporter and RIP assays and Pearson's correlation analysis were performed to evaluate relationships between genes. RESULTS: Circ-TFF1 and TFF1 were both upregulated and positively associated with each other in breast cancer. Knockdown of circ-TFF1 hindered breast cancer cell proliferation, migration, invasion and EMT in vitro and controlled tumour growth in vivo. Circ-TFF1 acted as a ceRNA of TFF1 by sponging miR-326, and its contribution to breast cancer progression was mediated by miR-326/TFF1 axis. CONCLUSIONS: Circ-TFF1 is a facilitator in breast cancer relying on TFF1 by absorbing miR-326, providing a novel promising target for BC treatment.