We have established a transgenic rat for
adenocarcinoma of the prostate (TRAP) model that features uniform
adenocarcinoma development in prostatic lobes at high incidence within a short experimental period. However, no invasive
carcinomas with reactive stroma characteristics similar to those in man were observed. We therefore have focused on a new model for invasive
carcinoma of the prostate using TRAP rats. In experiment 1, male TRAP rats in groups 1 and 2 were treated with
orchiectomy at day 0 of the experiment. Rats in groups 1-3 underwent
testosterone propionate (TP) implantation from weeks 1 to 4 and from weeks 6 to 16. Rats in groups 1 and 3 were given
3,2'-dimethyl-4-aminobiphenyl (DMAB) after TP implantation. The rats of group 4 served as controls. In experiment 2, the rats were divided into three groups, none of which received DMAB or
orchiectomy, treated with TP continuously or with the treatment withdrawn once or twice. In experiment 1, invasive
adenocarcinomas with abundant collagenous stroma were found in the dorsolateral and anterior prostate, some of which showed perineural space invasion at week 16. The number of invasive
carcinoma foci was most frequent in group 3. In experiment 2, invasive
adenocarcinoma development in the lateral prostates was correlated with the number of TP administration/withdrawal cycles. In conclusion, our newly established rat model for invasive
adenocarcinoma of the prostate could serve as a useful preclinical model for evaluating the in vivo efficacy of preventive and therapeutic agents targeting of the tumor microenvironment.