Beta Catenin in Prostate Cancer

描述（由申请人提供）：β -连环蛋白是Wnt信号通路的一个组成部分，在许多癌症类型中被致癌突变破坏。我们首先证明了-连环蛋白在前列腺癌标本的一个子集中发生突变。来自其他实验室的新数据证实了我们的发现，并确定了Wnt信号通路的其他成分（如前列腺癌中的APC）的突变。在前列腺癌细胞中，突变的β -连环蛋白可以增强雄激素受体（AR）信号传导并拓宽配体特异性。由于AR活性增加和对更多类固醇激素的反应是晚期前列腺癌的标志，β -连环蛋白突变似乎是前列腺癌细胞增强AR活性的另一种机制。这一发现可能对确定前列腺癌患者适当的二线激素治疗具有临床意义。我们现在建议阐明β -连环蛋白与雄激素受体之间直接分子间相互作用的细节。我们的初步数据表明β -连环蛋白与AR配体结合域结合。此外，β -catenin犰狳重复区的LXXLL肽基序与p160类固醇激素共激活因子分子中的基序相似，对β -catenin/ AR相互作用很重要。利用哺乳动物双杂交实验，我们将确定β -连环蛋白与雄激素受体结合的区域和β -连环蛋白与雄激素受体结合的区域。利用重组蛋白，我们将证明AR和β -连环蛋白之间的直接物理相互作用。我们还将确定这种结合的配体依赖性和支持相互作用的配体光谱。我们将通过测量不同配体与雄激素受体的解离来确定-连环蛋白是否影响雄激素受体与配体的相互作用。最后，我们将确定β -连环蛋白与p160类固醇受体辅激活蛋白协同增加AR活性的机制。这些实验将清楚地确定Wnt信号和类固醇受体途径之间的相互作用，从而描述前列腺癌进展的新机制，这通常依赖于AR活性的增强。

DESCRIPTION (provided by applicant): Beta-catenin is a component of the Wnt signaling pathway that is disrupted by oncogenic mutations in many cancer types. We first demonstrated that beta-catenin was mutated in a subset of prostate cancer specimens. Emerging data from other laboratories have confirmed our findings and identified mutations in other components of the Wnt signaling pathway such as APC in prostate cancer. In prostate cancer cells mutant beta-catenin can potentiate androgen receptor (AR) signaling and broaden ligand specificity. Since increased AR activity and response to an expanded range of steroid hormones is a hallmark of advanced prostate cancer, beta-catenin mutations appear to be an additional mechanism by which prostate cancer cells enhance AR activity. This finding may have clinical implications for determining apropriate second-line hormonal therapy for prostate cancer patients. We now propose to elucidate the details of the direct intermolecular interactions between beta-catenin and androgen receptor. Our preliminary data indicate that beta-catenin binds to the AR ligand-binding domain. Moreover, LXXLL peptide motifs in the beta-catenin armadillo repeat region that resemble motifs in p160 steroid hormone coactivator molecules are important for beta-catenin/ AR interaction. Using a mammalian two-hybrid assay we will determine the regions of androgen receptor bound by beta-catenin and we will determine the regions of beta-catenin that bind androgen receptor. Using recombinant proteins we will demonstrate the direct physical interaction between AR and beta-catenin. We will also determine the ligand-dependence of this binding and the spectrum of ligands that support the interaction. We will determine if beta-catenin affects the interaction of androgen receptor with ligand by measuring dissociation of different ligands from androgen receptor. Lastly, we will determine the mechanism by which beta-catenin synergizes with p160 steroid receptor coactivator proteins to increase AR activity. These experiments will clearly establish as interaction between the Wnt signaling and steroid receptor pathways and thereby describe a new mechanism for prostate cancer progression, which is often dependent on enhancement of AR activity.