Abstract
MicroRNAs (miRNAs/miRs) are 19-25 nucleotide-long, non-coding RNAs that regulate the expression of target genes at the post-transcriptional level. In the present study, the role of miR-340 in breast cancer (BC) was investigated. The overexpression of miR-340 significantly inhibited the proliferation, migration and invasion of human breast MDA-MB-231 cancer cells in vitro. The Rho-associated, coiled-coil containing protein kinase 1 (ROCK1) gene was identified as a target of miR-340; its expression was downregulated by overexpression of miR-340 by binding to its 3'-untranslated region. The short interfering RNA-mediated silencing of ROCK1 was also performed, which phenocopied the effects of miR-340 overexpression. An inhibitor of miR-340 was used to suppress miR-340 expression, which led to increased expression of ROCK1, thus improving the proliferation, migration and invasion of MDA-MB-231 cells. Data from the present study suggest that miR-340 inhibits MDA-MB-231 cell growth and its downregulation may lead to the progression and metastasis of BC. Thus, miR340 may act as a tumor-suppressor agent that could serve a key role in the diagnosis and therapy of BC.