Seewaldt V L, Mrózek K, Dietze E C, Parker M, Caldwell L E
Division of Medical Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Cancer Res. 2001 Jan 15;61(2):616-24.
Aberrant p53 expression is frequently observed in mammary epithelial cells obtained from women at high risk for developing breast cancer and is a predictor for the subsequent development of malignancy. Tamoxifen has recently been shown to reduce the incidence of noninvasive breast cancer in high-risk women, but the molecular mechanism of tamoxifen chemoprevention in mammary epithelial tissue that does not overexpress the estrogen receptor is poorly understood. We suppressed p53 expression by retroviral-mediated expression of human papillomavirus type-16 E6 protein (HPV-16 E6) in human mammary epithelial cells (HMECs) to develop an in vitro model of tamoxifen chemoprevention in the context of p53 loss. Early passage p53(-) HMEC-E6-transduced cells treated with 1.0 microM tamoxifen rapidly underwent apoptosis. In contrast, early passage p53(+) HMEC-LXSN vector controls treated with 1.0 microM tamoxifen underwent G1-G0-phase arrest but did not undergo apoptosis. p53(-) HMEC-E6 cells rapidly acquired resistance to tamoxifen-mediated apoptosis after 10 passages in culture (in the absence of tamoxifen). Both p53(+) and p53(-) HMECs exhibited a low level of estrogen receptor staining and minimal estrogen binding, characteristic of proliferating normal luminal mammary epithelial cells. Tamoxifen-mediated apoptosis in p53(-) HMEC-E6 cells was not blocked by inhibitors of transcription and protein synthesis. These data suggest that the acute loss of p53 function in HMECs by expression of HPV-16 E6 results in marked sensitivity to tamoxifen-mediated apoptosis but that resistance to apoptosis rapidly develops within 10 passages in vitro. Observations in our model system predict a critical role for the early institution of tamoxifen chemoprevention.
在患乳腺癌风险较高的女性的乳腺上皮细胞中经常观察到异常的p53表达，它是恶性肿瘤后续发展的一个预测指标。他莫昔芬最近已被证明可降低高危女性非浸润性乳腺癌的发病率，但对于他莫昔芬在未过表达雌激素受体的乳腺上皮组织中进行化学预防的分子机制了解甚少。我们通过逆转录病毒介导的人乳头瘤病毒16型E6蛋白（HPV-16 E6）在人乳腺上皮细胞（HMECs）中的表达来抑制p53表达，以建立一个在p53缺失情况下他莫昔芬化学预防的体外模型。用1.0微摩尔他莫昔芬处理的早期传代p53(-) HMEC-E6转导细胞迅速发生凋亡。相比之下，用1.0微摩尔他莫昔芬处理的早期传代p53(+) HMEC-LXSN载体对照进入G1-G0期停滞，但未发生凋亡。p53(-) HMEC-E6细胞在培养10代后（在无他莫昔芬的情况下）迅速获得对他莫昔芬介导凋亡的抗性。p53(+)和p53(-) HMECs均表现出低水平的雌激素受体染色和最小的雌激素结合，这是增殖的正常管腔乳腺上皮细胞的特征。他莫昔芬介导的p53(-) HMEC-E6细胞凋亡未被转录和蛋白质合成抑制剂阻断。这些数据表明，通过HPV-16 E6的表达使HMECs中p53功能急性丧失导致对他莫昔芬介导的凋亡具有显著敏感性，但在体外10代内对凋亡抗性迅速发展。我们模型系统中的观察结果预测了他莫昔芬化学预防早期实施的关键作用。
