Abstract: OBJECTIVE: To explore the roles of miR-21 in regulating migration and invasion of triplenegative breast cancer MDA-MB-231 cells via targeting PDCD4. METHODS: Quantitative real-time PCR (qPCR) was used to detect the expression of miR-21 and PDCD4 mRNA in MDA-MB-231 and MCF-10A cells. MDA-MB-231 cells were divided into five groups,including blank control,miR-21 mimics,miR-21 inhibitor, negative mimics and negative inhibitor. Western blotting was used to detect PDCD4 protein expression, and luciferase reporter gene assay was used to detect whether miR-21 was targeting PDCD4. Migration and invasion of MDA-MB-231 cells were detected using Transwell chambers. RESULTS: miR-21 and PDCD4 mRNA in MDA-MB-231 cells was significantly higher and lower than that of MCF-10A cells, respectively (P < 0.01). The overexpression or inhibition of miR-21 were concurrent with the up-or downregulation of PDCD4 expression. Luciferase reporter gene assays showed that PDCD4 was a direct target of miR-21. Transwell assays demonstrated that modulating miR-21 with mimics or inhibitors changed the migration and invasion of MDA-MB-231 cells. CONCLUSION: Migration and invasion of MDA-MB-231 cells were regulated by miR-21 through targeting PDCD4. Regulating the expression of miR-21 could be a novel target for inhibiting these invasive activities in triple-negative breast cancers.

Key words: triple-negative breast cancer, miR-21, PDCD4, migration, invasion