Circ_0000043 promotes the proliferation, migration, invasiveness, and epithelial–mesenchymal transition in breast cancer cells via the miR-136–Smad3 axis

Circular RNAs (circRNAs) are tissue-specific RNAs with a more stable structure than linear RNAs, and their association with breast cancer (BC) is poorly understood. This study examined the biological effects of circ_0000043 in the progression of BC. In this study, expression of circ_0000043 in BC tissue samples was measured using quantitative real-time polymerase chain reaction. Immunohistochemistry and Western blot were used to detect the expression of Smad family member 3 (Smad3). CCK-8, wound healing, and Transwell assays were used to assess the effect of circ_0000043 on the proliferation, migration, and invasiveness of BC cells. Moreover, the binding relationships between circ_0000043 and miR-136, and miR-136 and Smad3 were detected by dual-luciferase reporter assay. Additionally, Western blot was used to detect the expressions of markers related to epithelial–mesenchymal transition, including E-cadherin, N-cadherin, and vimentin. Our results show that the expression of circ_0000043 is up-regulated in BC tissues and cell lines. The proliferation, migration, invasiveness, and epithelial–mesenchymal transition of BC cells were significantly inhibited by knockdown of circ_0000043, and overexpression of circ_0000043 had the opposite effects. Additionally, circ_0000043 up-regulate the expression of Smad3 by sponging miR-136. In conclusion, our study demonstrates that circ_0000043 promote the progression of BC via regulating the miR-136–Smad3 axis.