Schultz Michelle A, Hagan Sharika S, Datta Amrita, Zhang Yiguo, Freeman Michael L, Sikka Suresh C, Abdel-Mageed Asim B, Mondal Debasis
Department of Pharmacology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America ; Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
Department of Urology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
PLoS One. 2014 Jan 22;9(1):e87204. doi: 10.1371/journal.pone.0087204. eCollection 2014.
Despite androgen deprivation therapy (ADT), persistent androgen receptor (AR) signaling enables outgrowth of castration resistant prostate cancer (CRPC). In prostate cancer (PCa) cells, ADT may enhance AR activity through induction of oxidative stress. Herein, we investigated the roles of Nrf1 and Nrf2, transcription factors that regulate antioxidant gene expression, on hormone-mediated AR transactivation using a syngeneic in vitro model of androgen dependent (LNCaP) and castration resistant (C4-2B) PCa cells. Dihydrotestosterone (DHT) stimulated transactivation of the androgen response element (ARE) was significantly greater in C4-2B cells than in LNCaP cells. DHT-induced AR transactivation was coupled with higher nuclear translocation of p65-Nrf1 in C4-2B cells, as compared to LNCaP cells. Conversely, DHT stimulation suppressed total Nrf2 levels in C4-2B cells but elevated total Nrf2 levels in LNCaP cells. Interestingly, siRNA mediated silencing of Nrf1 attenuated AR transactivation while p65-Nrf1 overexpression enhanced AR transactivation. Subsequent studies showed that Nrf1 physically interacts with AR and enhances AR's DNA-binding activity, suggesting that the p65-Nrf1 isoform is a potential AR coactivator. In contrast, Nrf2 suppressed AR-mediated transactivation by stimulating the nuclear accumulation of the p120-Nrf1 which suppressed AR transactivation. Quantitative RT-PCR studies further validated the inductive effects of p65-Nrf1 isoform on the androgen regulated genes, PSA and TMPRSS2. Therefore, our findings implicate differential roles of Nrf1 and Nrf2 in regulating AR transactivation in PCa cells. Our findings also indicate that the DHT-stimulated increase in p65-Nrf1 and the simultaneous suppression of both Nrf2 and p120-Nrf1 ultimately facilitates AR transactivation in CRPC cells.
尽管采用了雄激素剥夺疗法（ADT），但持续的雄激素受体（AR）信号传导仍能使去势抵抗性前列腺癌（CRPC）生长。在前列腺癌细胞中，ADT可能通过诱导氧化应激来增强AR活性。在此，我们使用雄激素依赖性（LNCaP）和去势抵抗性（C4-2B）前列腺癌细胞的同基因体外模型，研究了调节抗氧化基因表达的转录因子Nrf1和Nrf2在激素介导的AR反式激活中的作用。双氢睾酮（DHT）刺激的雄激素反应元件（ARE）反式激活在C4-2B细胞中显著高于LNCaP细胞。与LNCaP细胞相比，DHT诱导的AR反式激活与C4-2B细胞中p65-Nrf1更高的核转位相关。相反，DHT刺激抑制了C4-2B细胞中总Nrf2水平，但提高了LNCaP细胞中总Nrf2水平。有趣的是，siRNA介导的Nrf1沉默减弱了AR反式激活，而p65-Nrf1过表达增强了AR反式激活。随后的研究表明，Nrf1与AR发生物理相互作用并增强AR的DNA结合活性，这表明p65-Nrf1异构体是一种潜在的AR共激活因子。相反，Nrf2通过刺激抑制AR反式激活的p120-Nrf1的核积累来抑制AR介导的反式激活。定量RT-PCR研究进一步验证了p65-Nrf1异构体对雄激素调节基因PSA和TMPRSS2的诱导作用。因此，我们的研究结果表明Nrf1和Nrf2在调节前列腺癌细胞中AR反式激活方面具有不同作用。我们的研究结果还表明，DHT刺激引起的p65-Nrf1增加以及Nrf2和p120-Nrf1的同时抑制最终促进了CRPC细胞中的AR反式激活。
