Tight junctions （TJs） are essential components of cell connectivity, maintaining cell polarity, permeability, and adhesion, and participating in the regulation of cell proliferation and differentiation. The claudin （CLDN） family is integral to TJs, with Claudin 6 （CLDN6） being a key member. CLDN6 is a transmembrane protein found in tight junctions, featuring two extracellular loops and intracellular N- and C-terminal tails. CLDN6 modulates ion- and charge-specific permeability in the paracellular pathway of most epithelial tissues.CLDN6 is widely expressed in various tumors, including liver, ovarian, endometrial, and esophageal cancers, as well as atypical teratoid/rhabdoid tumors. Given its expression profile, CLDN6 has potential as a carcinoembryonic antigen and a therapeutic target.