CLDN1 and neoplasm: The epithelial–mesenchymal transition (EMT) was considered as a classic molecular mechanism of tumor metastasis, with remarkable changes in expression levels of several crucial EMT-related proteins, including zinc finger E-box binding homeobox (ZEBs) proteins, Snail proteins, matrix metalloproteinases (MMPs) proteins, Claudin-1, Vimentin, Cadherin-1 (CDH1), and Cadherin-2 (CDH2) which gained a lot of attention on the treatment for multiple cancers [27].