The tumor-suppressive function of miR-30a reverses EMT in breast cancer by directly targeting the 3′-UTR of Slug. In vitro binding of miR-30a to Slug mRNA increased expression of the tight-junction proteins CLDN-1, -2, and -3 and decreased the metastatic capability of those cells owing to its effects on the reduction of F-actin polymerization. The gene discussed is CLDN1; the disease is breast cancer.