To examine whether CLDN1 expression regulates EMT in breast cancer cells, we examined the expression of the epithelial cell marker, E-cadherin, and the mesenchymal markers, Vimentin, Snai2 and SMA, in both MDA-MB-231 and MCF7 stable cells transduced with two different CLDN1 lentiviral shRNA and SC control vectors. The gene discussed is CLDN1; the disease is breast carcinoma.