CLDN3 and prostate cancer: Regarding prostate cancer, prostate-specific membrane antigen (PSMA) has emerged as the best theranostic target,147 warranting multiple studies that used active targeting in the form of antibodies148 or even an innovative PSMA-targeting Glu-Urea-Lys scaffold.149 Martin et al.150 targeted claudin-3 and -4 using a non-toxic Clostridium perfringens enterotoxin, showing overexpression in high grade prostate cancers.