The tumor-suppressive microRNA-1/133a cluster targets PDE7A and inhibits cancer cell migration and invasion in endometrial cancer

In developed countries, endometrial cancer (EC) is the most common malignancy among women. Unopposed estrogen therapy, obesity, nulliparity, diabetes mellitus and arterial hypertension have been linked to an increased risk of EC. However, the molecular mechanisms of EC oncogenesis and metastasis have not yet been fully elucidated. Our recent studies of microRNA (miRNA) expression signatures revealed that the microRNA-1/133a (miR-1/133a) cluster is frequently downregulated in various types of human cancers. However, the functional role of the miR-1/133a cluster in EC cells is still unknown. Thus, the aim of this study was to investigate the functional significance of the miR-1/133a cluster and its regulated molecular targets, with an emphasis on the contributions of miR-1/133a to EC oncogenesis and metastasis. We found that the expression levels of miR-1 and miR-133a were significantly reduced in EC tissues. Moreover, restoration of mature miR-1 or miR-133a miRNAs significantly inhibited cancer cell migration and invasion, suggesting that these clustered miRNAs act as tumor suppressors. Prediction of miRNA targets revealed that phosphodiesterase 7A (PDE7A) was a potential target gene regulated by both miR-I and miR-133a. PDE7A was confirmed to be overexpressed in EC clinical specimens and silencing of PDE7A significantly inhibited cancer cell migration and invasion. Our data demonstrated that downregulation of the miR-1/133a cluster promoted cancer cell migration and invasion via overexpression of PDE7A in EC cells. Elucidation of the molecular networks regulated by tumor-suppressive miRNAs will provide insights into the molecular mechanisms of EC oncogenesis and metastasis.