CLDN4 and cancer: Although claudin-4 expression promoted by lncRNA-KRTAP5-AS1 and lncRNA-TUBB2A contributes to aggressive cancer behaviors in gastric cancer (102) and β-catenin expression is synchronous with claudin-4 upregulation in CAC tissues (55), there is also evidence showing that claudin-4 suppression in colorectal cancer tissues correlates with aggressive cancer behaviors (103).