Circ_0069094 regulates malignant phenotype and paclitaxel resistance in breast cancer cells via targeting the miR‐136‐5p/YWHAZ axis

BACKGROUND: Breast cancer is one of the most malignant cancers. Increasing evidence suggests that circular RNAs (circRNAs) are involved in breast cancer progression through sponging microRNA (miRNA). However, the underlying molecular mechanisms of circ_0069094 in breast cancer are unclear. This study aimed to reveal the effect of the circ_0069094/miR‐136‐5p/tyrosine 3‐monooxygenase/tryptophan 5‐monooxygenase activation protein zeta (YWHAZ) pathway on the malignant progression of breast cancer. METHODS: The quantitative real‐time polymerase chain reaction and western blot were used to assess the expression of circRNA/miRNA/mRNA. The functional effects of circ_0069094 on the cell processes of breast cancer were investigated by cell counting kit‐8, colony‐forming assay, 5‐ethynyl‐2′‐deoxyuridine (EdU) assay, flow cytometry, and transwell invasion assay. The interactions among circ_0069094, miR‐136‐5p, and YWHAZ were assessed by dual‐luciferase reporter assay. A xenograft experiment was performed to determine the effects of circ_0069094 on tumor formation. RESULTS: Circ_0069094 was overexpressed in paclitaxel (PTX)‐resistant breast cancer tissues and cells, and the silencing of circ_0069094 decreased tumor growth, cell proliferation and cell invasion while increasing PTX sensitivity and cell apoptosis in PTX‐resistant cells. In addition, miR‐136‐5p was a target of circ_0069094, and miR‐136‐5p inhibition abolished circ_0069094 knockdown‐induced effects in PTX‐resistant cells. MiR‐136‐5p expression was decreased in PTX‐resistant breast cancer tissues and cells, and the overexpression of miR‐136‐5p suppressed the malignant behaviors of breast cancer cells by targeting YWHAZ. Importantly, circ_0069094 regulated YWHAZ expression in breast cancer by targeting miR‐136‐5p. CONCLUSION: Circ_0069094 silencing improved PTX sensitivity in breast cancer progression through competitively sponging miR‐136‐5p.