Zhang Liqun, Johnson Mai, Le Kim H, Sato Makoto, Ilagan Romyla, Iyer Meera, Gambhir Sanjiv S, Wu Lily, Carey Michael
Departments of Biological Chemistry, University of California Los Angeles School of Medicine, Los Angeles, CA 90095, USA.
Cancer Res. 2003 Aug 1;63(15):4552-60.
The early androgen-dependent (AD) phase of prostate cancer is dependent on the androgen receptor (AR). However, it is unclear whether AR is fully functional in recurrent prostate cancer after androgen withdrawal. To address this issue we interrogated AR signaling in AD and recurrent prostate cancer xenografts using molecular imaging, chromatin immunoprecipitation, and immunohistochemistry. In the imaging experiments, an adenovirus bearing a two-step transcriptional activation cassette, which amplifies AR-dependent firefly luciferase reporter gene activity, was injected into tumors implanted into severe combined immunodeficiency mice. A charge-coupled device optical imaging system detected the initial loss and then resumption of AR transcriptional activity in D-luciferin-injected mice as tumors transitioned from AD to recurrent growth. The results of chromatin immunoprecipitation and immunohistochemical localization experiments correlated with the Ad two-step transcriptional activation imaging signal. AR localized to the nucleus and bound to the endogenous prostate-specific antigen enhancer in AD tumors but exited the nucleus and dissociated from the enhancer upon castration. However, AR reentered the nucleus and rebound the prostate-specific antigen enhancer as the cancer transitioned into the recurrent phase. Surprisingly, RNA polymerase II and the general factor TFIIB remained bound to the gene throughout the transition. Our data support the concept that AR is fully functional in recurrent cancer and suggest a model by which a poised but largely inactive transcription complex facilitates reactivation by AR at castrate levels of ligand.
前列腺癌的早期雄激素依赖（AD）阶段依赖于雄激素受体（AR）。然而，尚不清楚AR在雄激素撤除后的复发性前列腺癌中是否仍具有完整功能。为了解决这个问题，我们使用分子成像、染色质免疫沉淀和免疫组织化学方法，对AD期和复发性前列腺癌异种移植模型中的AR信号传导进行了研究。在成像实验中，将携带两步转录激活盒的腺病毒注射到植入重症联合免疫缺陷小鼠体内的肿瘤中，该转录激活盒可增强AR依赖的萤火虫荧光素酶报告基因活性。当肿瘤从AD期转变为复发性生长时，电荷耦合器件光学成像系统检测到在注射D-荧光素的小鼠中，AR转录活性最初丧失然后恢复。染色质免疫沉淀和免疫组织化学定位实验结果与腺病毒两步转录激活成像信号相关。在AD期肿瘤中，AR定位于细胞核并与内源性前列腺特异性抗原增强子结合，但去势后AR离开细胞核并与增强子解离。然而，随着癌症转变为复发阶段，AR重新进入细胞核并再次与前列腺特异性抗原增强子结合。令人惊讶的是，在整个转变过程中，RNA聚合酶II和通用因子TFIIB一直与该基因结合。我们的数据支持AR在复发性癌症中具有完整功能的概念，并提出了一个模型，即一个处于就绪状态但基本无活性的转录复合物在去势水平的配体作用下促进AR重新激活。
