The selective oestrogen receptor modulators idoxifene and raloxifene have fundamentally different cell-specific oestrogen-response element (ERE)-dependent/independent mechanisms in vitro.
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abstract
Idoxifene and raloxifene are selective oestrogen receptor modulators (SERMs) that by definition exhibit tissue-specific agonist or antagonist properties via interactions with the oestrogen receptor (ER). Idoxifene acts as an oestrogen agonist in osteoblastic cells via an ER/ERE-mediated mechanism. In contrast, raloxifene is an antagonist via the ERE in osteoblastic cells. Like the pure antagonist ICI 182,780, raloxifene inhibited the potent agonist activity of both 17beta-oestradiol and idoxifene through the ERE whereas idoxifene had no effect on the agonist activity of 17beta-oestradiol via the ERE. In breast cancer cells, both raloxifene and idoxifene were potent antagonists of ERE-mediated 17beta-oestradiol action suggesting an ERE-dependent mechanism of action for both ligands in these cells. Therefore, these SERMs exhibit cell-specific ERE-dependent and -independent mechanisms of action.
