MiR-31 inhibits migration and invasion by targeting SATB2 in triple negative breast cancer.

Metastasis is the leading cause of death among breast cancer (BCa) patients and triple negative breast cancer (TNBC) as one of BCa subtypes exhibits the worst survival rate due to its highly aggressive and metastatic behavior. A growing body of research has shown that the dynamic expression of microRNAs (miRNAs) was intimately associated with tumor invasion and metastasis. Recent studies have demonstrated miR-31 as a metastasis-suppressor in breast cancer, but it is still known little about the mechanism of it suppresses metastasis. The special AT-rich sequence-binding protein-2 (SATB2) has been reported to involve in tumor proliferation and invasion, but its function and relationship with miR-31 in breast cancer is still unknown. Here we found that the expression of miR-31 was downregulated in TNBC tissue and cell line. MiR-31 expression was increased after MDA-MB-231 cell was treated by 5-aza-2'-deoxycytidine (5-AZA-CdR), enhance the expression of miR-31 significantly inhibited MDA-MB-231 cell migration and invasion, downregulation of miR-31 expression could promoted MCF-7 cell migration and invasion. The expression of SATB2 was negatively correlated with miR-31 and was upregulated in MCF-7 and MDA-MB-231. Silencing SATB2 expression significantly inhibited MCF-7 and MDA-MB-231 cell proliferation, migration and invasion. Luciferase reporter assays indicated SATB2 is a direct target of miR-31. Taken together, these results suggest miR-31 inhibited TNBC cells migration and invasion through suppressing SATB2 expression.