Background: Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer in women globally. This subtype often has early and high recurrence rates, resulting in poor survival, partially due to lack of targeted therapies. To date, the detailed molecular mechanisms underlying TNBC progression are unclear. Given the crucial role of microRNAs (miRNAs) in cancer metastasis, we aimed to analyse the expression and function of a metastasis-associated miRNA named miR-211-5p in TNBC.
Methods: MiRNA array analysis was performed to search for metastasis-associated miRNAs in TNBC. The miR-211-5p expression in tumour tissues, adjacent non-tumourous breast tissues of TNBC patients and cell lines were evaluated by real-time PCR. The protein expression levels were analysed by western blot, immunohistochemistry and in situ hybridisation. Luciferase reporter assays were employed to validate the target of miR-211-5p. The effect of miR-211-5p on TNBC progression was investigated in vitro and in vivo.
Results: MiR-211-5p was significantly downregulated in TNBC, and its expression level was associated with overall survival in TNBC. The expression of miR-211-5p suppressed TNBC cell proliferation, invasion, migration and metastasis in vitro and in vivo. Furthermore, SETBP1 was identified as a target of miR-211-5p. Through gain-of-function and loss-of-function studies, SETBP1 was shown to significantly affect colony and cell number in vitro. Enforced expression of miR-211-5p inhibited the expression of SETBP1 significantly and the restoration of SETBP1 expression reversed the inhibitory effects of miR-211-5p on TNBC cell proliferation and metastasis.
Conclusions: These findings collectively demonstrate a tumour suppressor role of miR-211-5p in TNBC progression by targeting SETBP1, suggesting that miR-211-5p could serve as a potential prognostic biomarker and therapeutic target for TNBC.