Confirming the results of our previous studies in a co-culture model with synthesized Ovcar-3 cells we found a significant (p < 0.05) decrease of claudin 5 in HUVEC co-cultured with our human ovarian cancer cells, which was prevented by simultaneous treatment with the VEGF-inhibitor Flt1-Fc. Here, CLDN5 is linked to ovarian carcinoma.