Related Experiment Videos
Cellular and molecular mechanism of action of antiestrogens
Abstract:
The mechanism of action of tamoxifen and of 4-hydroxytamoxifen is reviewed at the cellular and molecular level, through the current view of the authors. Synthetic antiestrogens are mainly acting directly on breast cancer cells by interacting with the estrogen receptor (RE). They prevent estrogen action by competing with estrogens on the cytosol RE. The resulting complex is partially activated, leading to its nuclear localisation and a partial and dissociated stimulation of the expression of estrogen responsive genes. A defective and partial activation of RE induced by antiestrogen is shown in vitro by several alterations of the RE concerning the dissociation rate of ligands and the affinity for double-stranded DNA and for a monoclonal antibody against the RE. The explanation of the inhibition of tumor growth is more controversial, since the proliferation of estrogen responsive cells is not only regulated by estrogens but also by other hormones and factors. We present evidence of a direct effect of antiestrogen mediated by the RE, and discuss the mechanism of resistance to antiestrogen in RE positive breast cancer cells.
Insights
Tamoxifen and 4-hydroxytamoxifen interact with the estrogen receptor (RE) in breast cancer cells, partially blocking estrogen
Area of Science:
- Endocrinology
- Molecular Biology
- Oncology
Background:
- Tamoxifen is a widely used synthetic antiestrogen.
- Its mechanism of action involves interaction with the estrogen receptor (RE).
- Understanding this interaction is crucial for breast cancer treatment.
Purpose of the Study:
- To review the cellular and molecular mechanisms of tamoxifen and 4-hydroxytamoxifen.
- To elucidate their direct effects on breast cancer cells via the RE.
- To discuss mechanisms of resistance to antiestrogens.
Main Methods:
- Review of current literature on tamoxifen and 4-hydroxytamoxifen.
- Analysis of in vitro studies detailing RE alterations.
- Examination of factors influencing tumor growth beyond estrogen.
Main Results:
- Antiestrogens bind to the cytosol RE, forming a complex that translocates to the nucleus.
- This complex induces partial and dissociated stimulation of estrogen-responsive genes.
- In vitro studies show defective RE activation, affecting ligand dissociation, DNA binding, and antibody affinity.
Conclusions:
- Tamoxifen and 4-hydroxytamoxifen exert a direct effect on breast cancer cells through the RE.
- Tumor growth inhibition is complex, influenced by multiple factors.
- Mechanisms of antiestrogen resistance in RE-positive breast cancer warrant further investigation.