Song R X-D, Zhang Z, Mor G, Santen R J
Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
Apoptosis. 2005 May;10(3):667-78. doi: 10.1007/s10495-005-1903-2.
Postmenopausal women with estrogen receptor positive (ER(+)) breast cancer frequently respond paradoxically to estrogen administration with tumor regression. Using both LTED and E8CASS cells derived from MCF-7 breast cancer cells by long-term estrogen-deprivation, we previously reported that 17beta -estradiol (estradiol) is a powerful, pro-apoptotic hormone which kills the cancer cells through activation of the Fas/FasL death receptor pathway. We postulated that the mitochondrial interactive protein Bcl-2 might play a role in the regulation of estradiol-induced apoptosis in both LTED and E8CASS cells. In this study, we assessed estradiol effects on cell growth, proliferation and apoptosis. Additionally we investigated the effect of estradiol on caspase activation, NF-KB and Bcl-2 expression. The functional role of Bcl-2 in estradiol-induced apoptosis was further studied by knockdown or decrease of Bcl-2 with siRNA. Our results show that estradiol significantly inhibited cell growth primarily through a pro-apoptotic action involving caspase-7 and 9 activations (p < 0.01). Basal Bcl-2 and NF-KB levels were greatly elevated and estradiol decreased NF-KB, but not Bcl-2 expression. Knockdown of Bcl-2 expression with siRNA decreased the levels of this protein by 9 fold (p < 0.01). This reduction markedly sensitized both LTED and E8CASS cells to the pro-apoptotic action of estradiol, leading to a synergistic induction of apoptosis and a concomitant reduction in cell number (p < 0.01). Therefore, down-regulation of Bcl-2 synergistically enhanced estradiol-induced apoptosis in ER(+) postmenopausal breast cancer cells.
雌激素受体阳性（ER(+)）的绝经后乳腺癌女性患者常常对雌激素给药产生矛盾反应，即肿瘤出现消退。我们先前利用长期雌激素剥夺从MCF-7乳腺癌细胞衍生而来的LTED和E8CASS细胞进行研究，结果显示17β-雌二醇（雌二醇）是一种强大的促凋亡激素，它通过激活Fas/FasL死亡受体途径杀死癌细胞。我们推测线粒体相互作用蛋白Bcl-2可能在LTED和E8CASS细胞中雌二醇诱导的凋亡调节中发挥作用。在本研究中，我们评估了雌二醇对细胞生长、增殖和凋亡的影响。此外，我们研究了雌二醇对半胱天冬酶激活、核因子-κB（NF-κB）和Bcl-2表达的影响。通过小干扰RNA（siRNA）敲低或降低Bcl-2进一步研究Bcl-2在雌二醇诱导凋亡中的功能作用。我们的结果表明，雌二醇主要通过涉及半胱天冬酶-7和-9激活的促凋亡作用显著抑制细胞生长（p < 0.01）。基础Bcl-2和NF-κB水平大幅升高，雌二醇降低了NF-κB水平，但未降低Bcl-2表达。用siRNA敲低Bcl-2表达使该蛋白水平降低了9倍（p < 0.01）。这种降低显著增强了LTED和E8CASS细胞对雌二醇促凋亡作用的敏感性，导致协同诱导凋亡并伴随细胞数量减少（p < 0.01）。因此，Bcl-2的下调协同增强了ER(+)绝经后乳腺癌细胞中雌二醇诱导的凋亡。
