MicroRNA-154 inhibits growth and invasion of breast cancer cells through targeting E2F5.

Accumulating evidence suggested that microRNA-154 (miR-154) might play important roles in the development of various cancer types. However, the role of miR-154 in breast cancer progression remains largely unknown. Here, miR-154 expression level was measured via quantitative real-time RT-PCR (qRT-PCR) in 36 pairs of human breast cancer tissues and adjacent normal breast tissues and in a panel of human breast cancer cell lines. Cell proliferation, cycle, migration, and invasion were assessed by CCK8 assay, flow cytometer assay, wound healing assay and transwell invasion assay, respectively. Luciferase reporter assay and Western blot was used to verify E2F transcription factor 5 protein (E2F5) as a novel target gene of miR-154. Our results showed that miR-154 was frequently downregulated in breast cancer tissues and cell lines. Overexpression of miR-154 in MCF-7 cells significantly inhibited cell proliferation, migration, and invasion, and increased cell arrest at G0/G1 stage in vitro. E2F5 was identified as a target of miR-154, and its expression was inversely correlated with miR-154 expression in clinical breast cancer tissues. In addition, downregulation of E2F5 in MCF7 cells had similar effect on cell proliferation, cycle, migration and invasion by miR-154 induced. These findings indicate that miR-154 acts as a tumor suppressor by targeting E2F5, suggesting miR-154 as a potential therapeutic target for the treatment of breast cancer.