Inhibition of tumor angiogenesis activity in C3H mouse mammary tumor by medroxyprogesterone acetate.
The growth of the C3H mouse mammary tumor (MMT) is considered to be hormone independent. Medroxyprogesterone acetate (MPA) had no effect on the growth of transplanted autochthonous MMT or the colony-formation of MMT cells. The tumor angiogenesis factor (TAF) activity of tumor-extract prepared from C3H mouse with transplanted autochthonous MMT and injected with 0.67 mg of MPA (in vivo MPA group) and that prepared from the colony of MMT cells treated with 10(-6) M MPA (in vitro MPA group) was lower (100.0% and 9.8%) than those of the in vivo and in vitro cortisol groups (325.5% and 44.3%), and the in vivo and in vitro groups without treatment (393.5% and 46.8%), respectively. The fibroblast growth factor (FGF) activity of the in vivo and in vitro MPA groups was lower (23.7% and 2.7%) than those of the in vivo and in vitro cortisol groups (54.7% and 11.3%), and the in vivo and in vitro groups without treatment (49.6% and 11.3%), respectively. Therefore, MPA may reduce neovascularization induced by TAF and FGF, although it had no effect on the growth of this MMT, and it had a glucocorticoid action similar to that of cortisol.