Circular RNAs (circRNAs) are important non-coding RNAs that are reportedly involved in the progression of diverse human cancers through their action as a microRNA (miRNA) sponge. However, the exact roles of circRNAs in breast cancer (BC) remain largely unknown. The present data demonstrate the significantly upregulated expression of hsa_circ_0007534 circRNA in BC tissues and cell lines. In contrast, miR-593 expression was significantly downregulated. Knockdown of hsa_circ_0007534 inhibited BC cell proliferation, colony formation, and invasion, and promoted apoptosis in BC cells. Moreover, hsa_circ_0007534 was demonstrated to be a sponge of miR-593, and expression of miR-593 in BC cells was negatively correlated with hsa_circ_0007534. MUC19 expression was markedly increased in BC tissues and cell lines, and the 3'-UTR of MUC19 was targeted by miR-593. The expression of MUC19 was negatively regulated by miR-593 in BC cells. Our findings suggest an oncogenic role for hsa_circ_0007534 in BC by acting as a miR-593 sponge to promote MUC19 expression. (C) 2018 Elsevier Inc. All rights reserved.