Circ_0002113 facilitates adriamycin resistance and malignant development of breast cancer by completely binding to miR-653-5p to induce upregulation of SPIN1

Circular RNAs (circRNAs) are involved in various biological processes of human cancers. The aim of this study was to investigate the roles of circ_0002113 in regulating cancer progression and adriamycin (ADM) resistance of breast cancer (BC). The quantification of circ_0002113, microRNA-653-5p (miR-653-5p) and Spindlin 1 (SPIN1) was performed via reverse transcriptionquantitative polymerase chain reaction assay. Cell sensitivity was detected by Cell Counting Kit-8 assay. Colony formation assay and EdU assay were used to determine cell proliferation. Apoptosis detection was conducted through flow cytometry. Western blot was carried out to measure protein levels. Tumor xenograft model was established for in vivo research. The interaction analysis was implemented using dual-luciferase reporter assay and RNA immunoprecipitation assay. Circ_0002113 was highly expressed in ADM-resistant BC tissues and cells. Downregulation of circ_0002113 suppressed ADM resistance and BC cell proliferation but promoted apoptosis. ADM sensitivity was enhanced by silencing of circ_0002113 in vivo. Circ_0002113 exhibited target interaction with miR-653-5p, and the regulatory roles of circ_0002113 were partly achieved by targeting miR-653-5p. SPIN1 served as a target of miR-653-5p and circ_0002113 incurred the expression regulation of SPIN1 by sponging miR-653-5p. SPIN1 overexpression attenuated the inhibitory effects of miR-653-5p on ADM resistance and tumor development of BC cells. Circ_0002113 regulated the level of SPIN1 via miRNA sponging function for miR-653-5p, thus promoting ADM resistance and cancer progression of BC cells.