Identification of circ_0038632 as a Promoter of Breast Cancer through miR-520a-3p-Dependent Modulation of CDCA3

Objective. Emerging evidence proves the importance of circular RNAs (circRNAs) in many tumors, including breast cancer (BC). Here, we aimed to define a mechanism by which circ_0038632 regulates BC process. Methods. To quantify the expression of circ_0038632, miR-520a-3p and cell division cycle associated 3 (CDCA3), a quantitative real-time PCR or immunoblotting method was utilized. The relationships of circ_0038632/miR-520a-3p and miR-520a-3p/CDCA3 in BC cells were determined using RNA immunoprecipitation (RIP) experiment and luciferase reporter assay. The effects of the circ_0038632/ miR-520a-3p/CDCA3 cascade on cell biological phenotypes in vitro were examined by flow cytometry, EdU assay, cell counting kit 8 assay, transwell assay and wound healing assay. The function of circ_0038632 in tumorigenicity of BC cells in vivo was evaluated by xenograft experiments. Results. Circ_0038632 and CDCA3 were highly expressed and miR-520a-3p expression was hindered in human BC. Depletion of circ_0038632 weakened cell growth, motility, and invasiveness while promoted cell apoptosis. In terms of mechanism, miR-520a-3p targeted CDCA3, and circ_0038632 involved the post-transcriptional modulation of CDCA3 expression by working as a miR-520a-3p sponge. Silencing of miR-520a-3p could reverse the inhibitory functions of circ_0038632 depletion in BC cell malignant phenotypes. Re-expression of CDCA3 also overturned the suppressive effects of miR-520a-3p on BC cell malignant phenotypes. In addition, circ_0038632 depletion inhibited the growth of xenograft tumors in vivo. Conclusion. Taken together, circ_0038632 promotes breast carcinogenesis through the miR-520a-3p/CDCA3 regulatory cascade, indicating that circ_0038632 may be a potential target for BC treatment.