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Updated: Sep 3, 2026
Long-term Culture of Human Breast Cancer Specimens and Their Analysis Using Optical Projection Tomography
Published on: July 29, 2011
Interactions of antiestrogens with human breast cancer in long-term tissue culture
Abstract:
A variety of antiestrogens can be shown to antagonize estrogen action in animal model systems. Several of these compounds are useful in the management of metastatic human breast cancer. To further elucidate their mechanism of action, we studied several of these compounds using human breast cancer cell lines maintained in long-term tissue culture as a model system. Antiestrogens including tamoxifen (NSC-180973; ICI-46474), nafoxidine. CI-628, and clomiphene citrate inhibit macromolecular synthesis below control levels in two human breast cell lines. This effect is limited to cell lines which contain estrogen receptors. Simultaneous addition of as little as 1000-fold less estradiol prevents antiestrogen effects. Sequential addition of estrogen for up to 48 hours to cells incubated in antiestrogen reverses inhibition. If cells are continued in antiestrogen alone for more than about 3 days, inhibitory effects become irreversible. The cells detach from the surface of the culture vessel and are no longer viable. Tamoxifen competes with 3H-estradiol for specific receptor sites but with about a 100-fold lower apparent affinity. Direct binding of 3H-tamoxifen and 3H-estradiol to duplicate cytoplasmic extracts reveals equivalent numbers of binding sites but a 20-fold lower affinity for the antiestrogen. There is reasonable agreement between concentrations of tamoxifen which bind to receptor and concentrations which inhibit cells.
Insights
Antiestrogens like tamoxifen inhibit growth in human breast cancer cells by blocking estrogen receptors. This effect is reversible with estrogen, but prolonged antiestrogen treatment leads to irreversible cell death.
Area of Science:
- Endocrinology
- Oncology
- Cell Biology
Background:
- Antiestrogens are used to treat metastatic breast cancer.
- Their precise mechanism of action requires further elucidation.
- Human breast cancer cell lines in long-term culture serve as a valuable model system.
Purpose of the Study:
- To investigate the mechanism of action of various antiestrogens.
- To determine the role of estrogen receptors in antiestrogen efficacy.
- To examine the reversibility and irreversibility of antiestrogen effects on cancer cells.
Main Methods:
- Utilized human breast cancer cell lines in long-term tissue culture.
- Administered antiestrogens (tamoxifen, nafoxidine, CI-628, clomiphene citrate) and estradiol.
- Assessed macromolecular synthesis inhibition and cell viability.
- Performed competitive binding assays with radiolabeled estradiol and tamoxifen for estrogen receptors.
Main Results:
- Antiestrogens inhibited macromolecular synthesis in estrogen receptor-positive cell lines.
- Estradiol addition prevented or reversed antiestrogen-induced inhibition.
- Prolonged antiestrogen exposure (over 3 days) resulted in irreversible cell death.
- Tamoxifen competed with estradiol for estrogen receptors with lower affinity.
Conclusions:
- Antiestrogen efficacy is dependent on the presence of estrogen receptors.
- Estrogen can counteract antiestrogen effects, but prolonged exposure leads to irreversible damage.
- Tamoxifen's binding affinity to estrogen receptors correlates with its cellular inhibitory effects.
