CLDN4 and bladder transitional cell carcinoma: A claudin-low subtype, also known as the mesenchymal subtype [59], has also been reported in COAD and BLCA [58], which are also molecularly characterized by the loss of expression of CLDN3, CLDN4, CLDN7 (claudins 3, 4, and 7), CDH1 (E-cadherin), MUC1, and EPCAM, and gain of VIM (vimentin) and several other mesenchymal markers [58,59,60].