Ligand-independent activation of the androgen receptor by the differentiation agent butyrate in human prostate cancer cells.
Ligand-independent activation of the androgen receptor by the differentiation agent butyrate in human prostate cancer cells.
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发表时间：
2000-10
期刊：
影响因子：
11.2
通讯作者：
M. Sadar;M. Gleave
中科院分区：
文献类型：
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作者：
M. Sadar;M. Gleave
雄激素是一种有效的分化剂，通过雄激素受体（AR）与PSA基因上的雄激素反应元件（AREs）结合来启动转录，从而调节前列腺特异性抗原（PSA）基因的表达。然而，在缺乏雄激素的情况下，PSA基因表达会升高。这表明，要么在缺乏雄激素的情况下，通过PSA基因上的AREs激活AR以提高PSA基因的表达，要么刺激另一种作用于PSA启动子的转录因子。我们之前已经在体内证明了丁酸盐，一种导致细胞周期阻滞的分化剂，会增加去势动物的血清PSA水平。因此，为了确定丁酸盐诱导PSA的机制，我们使用LNCaP人前列腺癌细胞系。Northern分析和PSA报告质粒转染实验表明，丁酸盐在LNCaP细胞中诱导PSA基因表达。抗雄激素bicalutamide的应用阻断了丁酸盐对PSA mRNA的诱导，表明其机制依赖于AR。与这一结论一致的是，电迁移转移试验显示，丁酸盐处理细胞的核提取物增加了AR- are复合物的形成。此外，其他含有AREs的报告基因构建体也被丁酸盐诱导。Western blot分析显示，暴露于丁酸盐的细胞中AR蛋白的核水平增加，而整个细胞水平保持不变，这表明丁酸盐导致AR的核易位。因此，分化剂丁酸盐导致AR的配体非依赖性激活，从而增加人类前列腺癌细胞中分化标记物PSA的表达。
Androgens are potent differentiation agents that regulate prostate-specific antigen (PSA) gene expression via the androgen receptor (AR) that binds to androgen response elements (AREs) on the PSA gene to initiate transcription. However, in the absence of androgens, PSA gene expression can become elevated. This suggests that either the AR can be activated in the absence of androgen to elevate PSA gene expression through AREs on the PSA gene or that another transcription factor acting on the PSA promoter is stimulated. We have previously shown in vivo that butyrate, a differentiation agent that causes cell cycle arrest, increases serum PSA levels in castrated animals. Therefore, to determine the mechanism of butyrate induction of PSA, we used the LNCaP human prostate cancer cell line. Northern analyses and transfection experiments using a PSA reporter plasmid demonstrated induction of PSA gene expression by butyrate in LNCaP cells. Application of the antiandrogen bicalutamide blocked the induction of PSA mRNA by butyrate, suggesting a mechanism dependent on the AR. Consistent with this conclusion, electromobility shift assays showed increased AR-ARE complex formation with nuclear extracts from butyrate-treated cells. In addition, other reporter gene constructs that contain AREs were also induced by butyrate. Western blot analysis showed an increase in nuclear levels of AR protein in cells exposed to butyrate, whereas whole cell levels remained unchanged, suggesting that butyrate causes nuclear translocation of the AR. Thus, the differentiation agent butyrate causes ligand-independent activation of the AR to increase expression of the differentiation marker PSA in human prostate cancer cells.