Effect of Long-Term Estrogen Deprivation on Apoptotic Responses of Breast Cancer Cells to 17β-Estradiol

• Published in: JNCI : Journal of the National Cancer Institute 2001-11, Vol.93 (22), p.1714-1723
• Main Authors: Song, Robert X.-D., Mor, Gil, Naftolin, Fred, McPherson, Robert A., Song, Joon, Zhang, Zhenguo, Yue, Wei, Wang, JiPing, Santen, Richard J.
• Format: Article
• Language: English
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/93.22.1714

Background: High doses of estrogen can promote tumor regression in postmenopausal women with hormone-dependent breast cancer, but the mechanism is unknown. We investigated the molecular basis of this process by using LTED cells, which were derived by growing MCF-7 breast cancer cells under long-term (6–24 months) estrogen-deprived conditions. Methods: We treated LTED and MCF-7 cells with various concentrations of 17β-estradiol (estradiol) and assayed their growth by counting the cells and measured apoptosis by annexin V staining and DNA fragmentation. Using western blot analysis, we also examined the expression of the apoptosis-inducing system of the Fas death receptor protein and its ligand, FasL, in these cells. To assess the involvement of Fas and FasL in the induction of apoptosis in LTED cells, we used activating anti-Fas antibodies and the universal caspase inhibitor Z-VAD. Finally, we examined the expression of Fas protein in E8CASS and BSK3 cells, two other cell lines derived by depriving MCF-7 cells of estrogen long term, and the responses of these cells to high-dose estradiol. All statistical tests were two-sided. Results: High concentrations of estradiol (≥0.1 nM) resulted in a statistically significant, 60% reduction in the growth of LTED cells (P