In breast tissue, tamoxifen acts as an estrogen antagonist
. In other tissue, including vaginal tissue, tamoxifen has been reported to exert an estrogen-like response on vaginal cytology by a mechanism yet to be understood and not expected based upon its an anti-estrogen activity.
As a SERM, based on class effects, one would expect it to be an estrogen antagonist
in breast and estrogenic in bone.
(29) Because it is an estrogen antagonist
in both breast and uterine tissues, raloxifene does not increase the risk of uterine or breast cancer.
Of the two receptors, the binding affinity of GEN for ER-[beta] is about 20 times higher than that for ER-[alpha], indicating that GEN has been related with its action as chemopreventive activity resulting from an estrogen antagonist
. Several studies have reported that GEN significantly inhibited the growth, metastasis and angiogenesis of various types of cancer (Kim et al.
Antiestrogens 2 Structure- activity studies in a series of 3- aroyl- 2- arylbenzo [b]thiophene derivatives leading to [6hydroxy- 2- (4-hydroxyphenyl)benzo[b] thien- 3- yl][4- [2- (1- piperidinyl)ethoxy] phenyl]methanone hydrochloride(LY156758), a remarkable effective estrogen antagonist
with only minimal intrinsic estrogenicity.
Tamoxifen, for example, is an estrogen antagonist
for the breast, exhibiting a cytostatic effect on ER-positive breast cancer cells, slowing proliferation.
The AF-2 mutation in the E/F domain disrupts AF-2 but can be activated via the AF-1 function by the estrogen antagonist
ICI 182,780 (ICI) (Arao et al.
It is thought to have a weak estrogenlike effect, as well as estrogen antagonist
This estrogen-elicited event is not abrogated by the estrogen antagonist
, ICI 182, 780, confirming its independence from the presence of estrogen receptor a (Lareef et al., 2005; Mello et al., 2007a).
Tamoxifen, a nonsteroidal estrogen antagonist
, is the endocrine treatment of choice to prevent breast cancer recurrence in women with positive estrogen receptors.
A complete estrogen antagonist
in the uterus, raloxifene was initially put on the shelf after a phase II trial showed that it caused no response in women with metastatic breast cancer refractory to tamoxifen, he said.
(1) Others, citing more recent research, have identified tamoxifen as an estrogen antagonist
, that is, a chemical which directly interferes with estrogen itself.