The transition of the cellular phenotype into mesenchymal expressing Snail or Slug has been associated with unfavorable prognosis in BC, which is commonly accompanied by the downregulation of claudin-1, a major constituent of the tight junction complexes; it was hence concluded that the claudin-low BC subtype is in fact a tumor manifesting mesenchymal features with Snail and Slug overexpression (18). Here, CLDN1 is linked to breast cancer.