Inhibition of miR‑214 attenuates the migration and invasion of triple‑negative breast cancer cells.

Triple‑negative breast cancer (TNBC) is a subtype of breast cancer. MicroRNA (miR)‑214 is closely associated with controlling the development of tumor cells; therefore, in the present study, the target gene and effects of miR‑214 on TNBC cells were explored. Luciferase activity was examined by luciferase reporter assay. The viability, invasion and migration of MDA‑MB‑231 TNBC cells were measured using Cell Counting kit‑8, Transwell and wound‑healing assays, respectively. The expression levels of various factors were determined using reverse transcription‑quantitative polymerase chain reaction and western blotting. The results demonstrated that the expression levels of miR‑214 were higher and the levels of α1‑antitrypsin (α1‑AT) were lower in TNBC tissues compared with in normal tissues. Subsequently, α1‑AT was revealed to be a target of miR‑214. Furthermore, inhibition of miR‑214 decreased cell viability, invasion and migration, enhanced the expression of E‑cadherin and tissue inhibitor of metalloproteinases‑2, and reduced the expression of metastatic tumour antigen 1 and matrix metalloproteinase‑2. Inhibition of miR‑214 also significantly downregulated the phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR), and markedly downregulated that of phosphoinositide 3‑kinase (PI3K); however, the expression levels of total PI3K, Akt and mTOR remained stable in all groups. Taken together, these findings indicated that α1‑AT may be a target of miR‑214. Downregulation of miR‑214 markedly suppressed the viability, migration and invasion of MDA‑MB‑231 cells, and inhibited the PI3K/Akt/mTOR pathway. These findings suggested that miR‑214 targeting α1‑AT may be a potential mechanism underlying TNBC development.