Hsa_circ_0025202 suppresses cell tumorigenesis and tamoxifen resistance via miR-197-3p/HIPK3 axis in breast cancer

BACKGROUND: The involvement of circular RNAs (circRNAs) in tamoxifen (TAM) resistance has been identified. Herein, we aimed to identify the role and novel mechanisms of hsa_circ_0025202 in tamoxifen resistance in breast cancer (BC). METHODS: The levels of hsa_circ_0025202, microRNA (miR)-197-3p, and homeodomain-interacting protein kinase 3 (HIPK3) were tested using quantitative real-time polymerase chain reaction and western blot. IC(50) value of TAM, cell proliferation, cell cycle, cell invasion, migration, apoptosis, western blot, and mouse xenograft assays was used to demonstrate the effects of hsa_circ_0025202, miR-197-3p, and HIPK3 on BC cell tumorigenesis and TAM resistance. Dual-luciferase report and RNA immunoprecipitation assays were applied to explore the potential interaction between miR-197-3p and hsa_circ_0025202 or HIPK3. RESULTS: Hsa_circ_0025202 was decreased in BC tissues and TAM resistant BC cells, and knockdown of hsa_circ_0025202 elevated the IC(50) value of cells to TAM, led to the promotion of cell proliferation, invasion and migration, mediated cell cycle progression, and inhibited cell apoptosis in BC in vitro. Besides, the upregulation of hsa_circ_0025202 hindered tumor growth and promoted TAM sensitivity in vivo. In a mechanical study, hsa_circ_0025202 targeted miR-197-3p, and silencing of miR-197-3p reversed the regulatory effects of hsa_circ_0025202 knockdown on TAM resistance and malignant phenotypes. Additionally, HIPK3 was a target of miR-197-3p, and miR-197-3p overexpression enhanced TAM resistance and promoted cell malignant biological behaviors in BC by targeting HIPK3. CONCLUSION: Hsa_circ_0025202 repressed cell tumorigenesis and TAM resistance via miR-197-3p/HIPK3 axis in BC, suggesting a potential therapeutic strategy to overcome chemoresistance in BC patients.