KLK3 and Familial prostate cancer: In a similar perspective, more recently Peng et al. [21] have investigated the use of a chimeric modified enhancer/promoter of the human prostate-specific antigen (PSA) gene to regulate the expression of a DT-A-encoding DNA both in vitro in transfected human prostate cancer cells and in vivo xenografts derived from these tumor cells, as well as within tumors in TRAMP mice model.