CLDN4 and ovarian neoplasm: In agreement with our results, HEY cells that do not express CLDN3 and CLDN4 also do not express E-cadherin, which may explain why the HEY cell line was the most aggressive among 5 ovarian tumor lines tested [62] and indicates that CLDN3 and CLDN4-dependent transcriptional regulation of E-cadherin may already exist in these cells.