CLDN3 and CLDN4 expression is regulated by DNA methylation and histone deacetylation, as shown by Honda et al., who examined ovarian cancer cells and noted that cells overexpressing CLDN3 and CLDN4 had low DNA methylation and high histone H3 acetylation of the critical promoter region of CLDN4 [138,139]. This evidence concerns the gene CLDN4 and ovarian cancer.