Development of Androgen‐independent Carcinomas from Androgen‐dependent Preneoplastic Lesions in the Male Accessory Sex Organs of Rats Treated with 3,2′‐Dimethyl‐4‐aminobiphenyl and Testosterone Propionate

Two kinds of cancer can be induced in rat male accessory sex organs, one a non‐invasive carcinoma arising in the ventral lobe and the other an invasive lesion which develops in the dorsolateral and anterior lobe as well as the seminal vesicles. In the present study, one group of male rats were given biweekly s.c. injections of 3,2′‐dimethyl‐4‐aminobiphenyl (DMAB) for 20 weeks for induction of non‐invasive carcinomas and the other group received DMAB with 40‐week testosterone propionate for induction of invasive carcinomas. Half of the animals in each group were then subjected to bilateral orchiectomy at week 41 to remove testicular androgen, in order to examine the androgen dependence of both types of carcinomas as well as precancerous lesions. Animals were killed at weeks 41, 46 and 60. All parts of the prostate complex showed involution and significant weight reduction after castration, with a complete disappearance of atypical hyperplasias and carcinomas of the ventral prostate. However, in spite of suppression of development of atypical hyperplasias in the anterior prostate and seminal vesicles, the incidence of invasive carcinomas was not changed. Normal epithelial cells and atypical hyperplasias of all parts of the prostate and seminal vesicles and carcinomas of the ventral prostate were immunohistochemically positive for nuclear androgen receptor, while invasive carcinomas that developed in either castrated or non‐castrated animals were negative. These findings suggest that in the ventral prostate, both precancerous and cancerous lesions are androgen‐dependent, but in the anterior and seminal vesicles, cancerous lesions (invasive carcinomas) are androgen‐independent while precancerous lesions are hormone‐dependent.