Immunohistochemically demonstrated androgen receptor expression in the rat prostate during carcinogenesis induced by 3,2′-dimethyl-4-aminobiphenyl with or without testosterone

A polyclonal antibody against rat androgen receptor was used to investigate its expression during 3,2′-dimethyl-4-aminobiphenyl (DMAB)-induced prostate carcinogenesis in the rat. Fixation in cold-acetone provided better observation of specific nuclear staining than 10% buffered formalin. Normal epithelial cells and atypical hyperplasias in all lobes were positive. Ventral prostate carcinomas were also strongly positive for androgen receptor (AR) but most invasive carcinomas arising from the dorsolateral prostate and seminal vesicles, which were induced by DMAB plus testosterone propionate, were AR negative. Atypical hyperplasias of those organs were all positive. These findings suggest that ventral carcinomas are androgen dependent but carcinomas in other lobes become independent during progression.