Effects of hexestrol, medroxyprogesterone acetate and chlormadinone acetate on 7, 12-dimethylbenz [a] anthracene-induced rat mammary cancer in relation to estrogen receptor.
The effects of hexestrol (HXS), medroxyprogesterone acetate (MAP) and chlormadinone acetate (CMA) on 7, 12-dimethylbenz [a] anthracene-induced mammary cancer in rats were evaluated. As a result of successive intramuscular injections of HXS at dosages of 2 or 10 mg/kg or MAP at dosages of 24 or 120 mg/Kg, tumors were markedly reduced in size in all groups on day 7 approximately 14. These effects were the same regardless of the presence or absence of cytoplasmic estrogen receptors (ER) in tumors as determined by the dextran-coated charcoal method. Although such an effect was also seen with CMA, it was much less marked than the effects seen with HXS and MAP. The body weights of HXS-administered groups decreased considerably, whereas those of MAP-administered groups increased. These results may suggest that there is another endocrinological tumor-suppressing mechanism besides the mechanism involving the estrogen-ER system in large-dose administration of HXS and MAP.