Raloxifene inhibits estrogen-induced up-regulation of telomerase activity in a human breast cancer cell line
Raloxifene inhibits estrogen-induced up-regulation of telomerase activity in a human breast cancer cell line
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DOI：
10.1074/jbc.m304363200
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发表时间：
2003-10-31
影响因子：
4.8
通讯作者：
Kurachi, H
中科院分区：
文献类型：
--
作者：
Kawagoe, J;Ohmichi, M;Kurachi, H
雷洛昔芬在乳腺癌化学预防中的作用机制仍不清楚。由于端粒酶活性参与雌激素诱导的癌变，因此我们研究了雷洛昔芬对 MCF-7 人乳腺癌细胞系中雌激素诱导的端粒酶活性上调的影响。 Raloxifene 抑制 17β-雌二醇 (E2) 诱导的细胞生长和端粒酶活性。雷洛昔芬抑制 E2 诱导的人端粒酶催化亚基 (hTERT) 的表达，使用含有 hTERT 启动子各种片段的荧光素酶报告质粒进行的瞬时表达测定表明，雌激素反应元件似乎对雷洛昔芬的作用负有部分责任。 E2 诱导 Akt 磷酸化，用磷脂酰肌醇 3-激酶 (PI3K) 抑制剂 LY294002 进行预处理，可减弱 E2 诱导的端粒酶活性和 hTERT 启动子活性的增加。雷洛昔芬抑制 E2 诱导的 Akt 磷酸化。此外，雷洛昔芬还通过 PI3K/Akt/NFkappaB 级联抑制 E2 诱导的 hTERT 表达。此外，雷洛昔芬还抑制 E2 诱导的 hTERT 磷酸化、NFkappaB 与 hTERT 的结合以及 hTERT 的核积累。这些结果表明，雷洛昔芬不仅通过雌激素响应元件依赖性机制和 PI3K/Akt/NFkappaB 级联对 hTERT 进行转录调节，而且通过 hTERT 磷酸化和与 NFkappaB 关联进行翻译后调节，抑制 E2 诱导的端粒酶活性上调。
The mechanism by which raloxifene acts in the chemoprevention of breast cancer remains unclear. Because telomerase activity is involved in estrogen-induced carcinogenesis, we examined the effect of raloxifene on estrogen-induced up-regulation of telomerase activity in MCF-7 human breast cancer cell line. Raloxifene inhibited the induction of cell growth and telomerase activity by 17beta-estradiol (E2). Raloxifene inhibited the E2-induced expression of the human telomerase catalytic subunit ( hTERT), and transient expression assays using luciferase reporter plasmids containing various fragments of the hTERT promoter showed that the estrogen-responsive element appeared to be partially responsible for the action of raloxifene. E2 induced the phosphorylation of Akt, and pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, attenuated the E2-induced increases of the telomerase activity and hTERT promoter activity. Raloxifene inhibited the E2-induced Akt phosphorylation. In addition, raloxifene also inhibited the E2-induced hTERT expression via the PI3K/Akt/NFkappaB cascade. Moreover, raloxifene also inhibited the E2-induced phosphorylation of hTERT, association of NFkappaB with hTERT, and nuclear accumulation of hTERT. These results show that raloxifene inhibited the E2-induced up-regulation of telomerase activity not only by transcriptional regulation of hTERT via an estrogen-responsive element-dependent mechanism and the PI3K/Akt/NFkappaB cascade but also by post-translational regulation via phosphorylation of hTERT and association with NFkappaB.