circ_0000515 promotes invasion and migration of breast cancer by attenuating MDM2-mediated FUS ubiquitination and degradation

Abstract Background : Breast cancer (BC) is the second lethal cancer with the highest and rising morbidity in females. Emerging evidences have illustrated that circular RNAs (circRNAs) play essential roles in the tumorigenesis and metastasis of BC. However, the specific functions and underlying mechanistic involvement of circ_0000515 in BC have not yet been explored. Methods : Three BC datasets (GES101123, GES165884, and GES182471) from the NCBI GEO database were screened to identify differentially expressed circRNAs (DEcircRNAs). Then transwell and wound healing assays were performed to determinethe function of circ_0000515 in BC. The identification of downstream targets of circ_0000515 was performed using bioinformatics methods. RNA-pulldown assays, RIP assay, and CO-IP were further employed to identify the critical signaling pathway regulated by circ_0000515. Finally, rescue experiments were employed to confirm the connection between circ_0000515 and FUS in BC metastasis. Results : Circ_0000515 of a total of 49 DEcircRNAs was identified in BC datasets. Interestingly, the abundance of circ_0000515 was significantly increased in BC cells. Loss-of-functional experiments in vitro showed silencing circ_0000515 inhibited the invasion, migration and EMT process of BC. Mechanically, circ_0000515 stabilized the expression of FUS by impeding the interplay between FUS and MDM2, thereby protecting FUS from proteasomal degradation. Interestingly, we identified that FUS knockdown dramatically alleviated the promotive effect of circ_0000515 on BC metastasis. Conclusion : Circ_0000515 promoted invasion and migration of BC by attenuating MDM2-mediated FUS ubiquitination and degradation, and might function as a biomarker and therapeutic target for BC.