We have previously shown that transforming growth factor β (TGFβ) is a hormonally regulated negative growth factor in estrogen responsive MCF-7 human breast cancer cells. We have now compared the antiestrogens tamoxifen, droloxifene (3-hydroxytamoxifen), and toremifene in their ability to induce the secretion of autoinhibitory TGFβ by MCF-7 cells. The main results are as follows: induction of TGFβ secretion by droloxifene is about two to three times higher than by identical concentrations of tamoxifen or toremifene. A 5-10 times higher concentration of tamoxifen or toremifene than droloxifene is necessary to reach a similar induction of TGFβ secretion. In contrast to tamoxifen, intermittent application of droloxifene is as effective as continuous treatment in inducing TGFβ secretion. We conclude from these data that TGFβ proteins represent markers of antiestrogen action and might also play a pivotal role in their mechanism of action. Droloxifene is a more effective inducer of TGFβ and a more potent growth inhibitor for estrogen responsive human breast cancer cells than tamoxifen and toremifene in vitro. Therefore, droloxifene might also possess a higher antiestrogenic potential in treatment of human breast cancer.
|Original language||English (US)|
|Journal||American Journal of Clinical Oncology: Cancer Clinical Trials|
|Issue number||SUPPL. 2|
|State||Published - 1991|
ASJC Scopus subject areas
- Cancer Research