In the present study we examined the effect of knocking down the expression of either CLDN3 or CLDN4 on known markers of EMT and report here that CLDN3 and CLDN4 suppression promotes EMT in ovarian cancer cells as reflected by a marked decrease in E-cadherin, up-regulation of Twist and activation of the PI3K/AKT pathway. This evidence concerns the gene CLDN4 and ovarian cancer.