Tamoxifen but not 4-hydroxytamoxifen initiates apoptosis in p53(-) normal human mammary epithelial cells by inducing mitochondrial depolarization
Tamoxifen but not 4-hydroxytamoxifen initiates apoptosis in p53(-) normal human mammary epithelial cells by inducing mitochondrial depolarization
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DOI：
10.1074/jbc.m007915200
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发表时间：
2001-02-16
影响因子：
4.8
通讯作者：
Seewaldt, VL
中科院分区：
文献类型：
--
作者：
Dietze, EC;Caldwell, LE;Seewaldt, VL
尽管他莫昔芬作为乳腺癌预防剂在临床上广泛使用，但人们对他莫昔芬化学预防的分子机制知之甚少。 p53 的异常表达被认为是乳腺癌发生的早期事件。我们开发了一种早期乳腺癌预防的体外模型，以研究他莫昔芬和 4-羟基他莫昔芬如何在 p53 功能严重丧失的正常人乳腺上皮细胞 (HMEC) 中发挥作用。 p53 功能受到逆转录病毒介导的人乳头瘤病毒 16 型 E6 蛋白表达的抑制。他莫昔芬（而非 4-羟基他莫昔芬）迅速诱导 p53(-) HMEC-E6 细胞凋亡，这一点可通过特征性形态变化、膜联蛋白 V 结合和 DNA 断裂来证明。我们观察到，在他莫昔芬处理的早期传代 p53(-) HMEC-E6 细胞中，线粒体膜电位、线粒体浓缩和 caspase 激活的降低先于细胞凋亡的形态学出现，p53(-) HMEC-E6 细胞在体外传代 10 次内迅速对他莫昔芬介导的细胞凋亡产生抵抗。晚期 p53(-) HMEC-E6 细胞对他莫昔芬的耐药性与他莫昔芬治疗后线粒体质量的增加以及线粒体去极化和 caspase 激活的缺乏相关。我们假设他莫昔芬诱导细胞凋亡的早期事件涉及线粒体去极化和半胱天冬酶激活，这对于有效的化学预防可能很重要。
Despite the widespread clinical use of tamoxifen as a breast cancer prevention agent, the molecular mechanism of tamoxifen chemoprevention is poorly understood. Abnormal expression of p53 is felt to be an early event in mammary carcinogenesis. We developed an in vitro model of early breast cancer prevention to investigate how tamoxifen and 4-hydroxytamoxifen may act in normal human mammary epithelial cells (HMECs) that have acutely lost p53 function. p53 function was suppressed by retrovirally mediated expression of the human papillomavirus type 16 E6 protein. Tamoxifen, but not 4-hydroxytamoxifen, rapidly induced apoptosis in p53(-) HMEC-E6 cells as evidenced by characteristic morphologic changes, annexin V binding, and DNA fragmentation. We observed that a decrease in mitochondrial membrane potential, mitochondrial condensation, and caspase activation preceded the morphologic appearance of apoptosis in tamoxifen-treated early passage p53(-) HMEC-E6 cells, p53(-) HMEC-E6 cells rapidly developed resistance to tamoxifen-mediated apoptosis within 10 passages in vitro. Resistance to tamoxifen in late passage p53(-) HMEC-E6 cells correlated with an increase in mitochondrial mass and a lack of mitochondrial depolarization and caspase activation following tamoxifen treatment. We hypothesize that an early event in the induction of apoptosis by tamoxifen involves mitochondrial depolarization and caspase activation, and this may be important for effective chemoprevention.