Abstract
MicroRNAs (miRNAs) are expressed aberrantly in various types of cancer, and negatively regulate the expression of target genes which may be useful in therapeutic strategies in several biological processes. In the present study, the expression levels and the effects of miRNA (miR)‑421 in breast cancer tissues and MCF‑7 and MDA‑MB‑231 cells were evaluated to elucidate therapeutic targets in breast cancer cells. The putative targets of miR‑421 were predicted by bioinformatics approaches, and the expression levels of miR‑421 were measured in MCF‑7 and MDA‑MB‑231 cells by reverse transcription‑quantitative polymerase chain reaction analysis following miR‑421 knockdown. The rates of cell proliferation, migration capacity, invasiveness and apoptosis were determined in miR‑421 inhibitor‑transfected MCF‑7 and MDA‑MB‑231 cells. The expression levels of target proteins regulated by miR‑421 in MCF‑7 and MDA‑MB‑231 cells were analyzed by western blot analysis. miR‑421 was increased significantly in breast cancer tissues and cells, and was regulated by miR‑421 antisense oligonucleotides. The knockdown of miR‑421 in MCF‑7 and MDA‑MB‑231 cells decreased cell proliferation, migration capacity and invasiveness, and promoted apoptosis compared with control groups. The expression of target protein programmed cell death 4 (PDCD4) were decreased in MCF‑7 and MDA‑MB‑231 cells transfected with miR‑421 inhibitors. These results suggested a correlation between miR‑421 and PDCD4, and physiological functions of breast cancer cells, suggesting that miR‑421 may be a potential strategy in the therapy of breast cancer.