Sex hormone receptors in mammary tumours of GR mice.

Studies of the growth behaviour and hormone receptor contents of GR-mouse mammary tumours suggest that the hormone responsive tumours are mixed populations of hormone-dependent cells and autonomous cells. The hormone-dependent moiety of these tumours contains high levels of progesterone receptor and oestrogen receptor. The autonomous moiety has a low but probably significant oestrogen receptor level, and is practically devoid of progesterone receptor. Androgen receptor levels in both moieties are low. Endocrine ablation prevents growth of the hormone-dependent moiety of the tumours, but not of the autonomous moiety.