MiRNA-20a-5p promotes the growth of triple-negative breast cancer cells through targeting RUNX3.

Increasing evidence showed that microRNAs (miRNAs) were abnormally expressed in cancers and made effects on the tumorigenesis. Aberrant expression of miR-20a-5p has been reported in human breast carcinoma. However, the functional mechanism of miR-20a-5p in human breast carcinoma, particularly in triple-negative breast cancer (TNBC), required further investigations. Here, firstly, we determined that miR-20a-5p was highly expressed in both TNBC tissues and cell lines. Then, we explored that the overexpression of miR-20a-5p promoted the migration and invasion of TNBC cells in vitro. The tendency was significantly reversed after the depletion of miR-20a-5p. Consistent result could be obtained with the in vivo nude mice tumorigenesis. Thirdly, the underlying molecular mechanism was investigated. The Runt-related transcription factor 3 (RUNX3) was identified as a target of miR-20a-5p in TNBC cells. High expression of miR-20a-5p significantly decreased both the mRNA and protein levels of RUNX3, as well as its direct downstream targets Bim and p21. These results verified the significance of miR-20a-5p and explored its functional mechanisms in TNBC, suggesting the potential clinical applications of miR-20a-5p in TNBC.