DMBA is ineffective in inducing breast cancer in feminized male Holtzman rats

Mammary tissue of male rats "feminized" by in utero treatment with cyproterone acetate, accrues the capacity to convert circulating androgens to estrogens at the mammary tissue level in adult life. DMBA-induced mammary tumorigenesis was studied in these feminized males to find out whether or not this altered steroid metabolism leading to heightened estrogenicity would increase mammary tumor yield when compared to that seen in normal males, where such conversion is significantly low. Results on the incidence of mammary tumors, tumor pathology and latency period of tumor appearance in these 2 groups, however, do not differ significantly. From observations on mammary morphology of these feminized males it appears that in vivo conversion of testosterone to estrogen probably is not total and that the available testosterone inhibits tumor induction.