Sex steroids as a cause of adenocarcinoma of the dorsal prostate in Nb rats, and their influence on the growth of transplants.

The development of adenocarcinoma of the dorsal prostate of Nb rats following prolonged treatment with pellets of testosterone propionate alone or with esterone allowed the establishment of transplantable tumor models. Whereas most transplants were autonomous and not influenced by hormones, one estrogen dependent tumor was studied in detail. This tumor would only grow in estrogenised hosts, cells remaining dormant in normal animals. Removal of estrogen from animals with growing tumors led to tumor regression but with progression and eventual regrowth of tumors which were autonomous. Replacement with lower doses of estrogen reduced the extent of regression and prevented autonomous change. When a regressed estrogen dependent tumor was exposed to prolonged treatment with testosterone propionate pellets, the eventual regrowth was found to be androgen dependent and would not grow in estrogenised animals. Progression could apparently be directed by this procedure from estrogen to androgen dependency.