CircUBR5 acts as a ceRNA for miR-1179 to up-regulate UBR5 and to promote malignancy of triple-negative breast cancer

UBR5 is an E3 ubiquitin ligase and an oncogene in a panel of human cancers. However, little is known on its impacts in triple-negative breast cancer (TNBC) and even less on its relationship to circUBR5 (hsa_circ_0001819), a circular RNA derived from exons 2, 3, 4, and 5 of UBR5 gene. In this study, we detected higher expressions of both circUBR5 and UBR5 in TNBC tissues, which were associated with worse prognosis, and also in a panel of breast cancer cells, particularly in TNBC cells. Functionally, circUBR5 was crucial for sustaining the malignant growth and metastasis of TNBC cells both in vitro and in vivo . Mechanistically, the oncogenic phenotypes of circUBC5 were mediated through sponging miR-1179 and up-regulating UBR5. Concomitant silencing circUBR5 and miR-1179 abolished the anti-tumor effects of targeting circUBR5 alone. Therefore, targeting circUBR5/miR-1179/UBR5 axis may benefit the treatment of TNBCs.