CLDN4 and ovarian cancer: CLDN3 and CLDN4, which are Clostridium perfringens enterotoxin (CPE) receptors, affected chemoresistance mediated by CPE in ovarian cancers [22, 23], it was also reported that CLDN3 and CLDN4 modulated the sensitivity to cisplatin partially through the copper and cisplatin influx transporter CTR1 [25].