CLDN4 and ovarian serous cystadenocarcinoma: EGF was found to downregulate claudin-3 in mucinous ovarian carcinoma cell lines and claudin-4 in ovarian serous cystadenocarcinoma by inducing the degradation of these proteins with also changes in the structure and function of TJ via the MEK/ERK or PI3K/AKT signaling pathway.