Significance of an novel germline AR mutation in black men with prostate cancer

描述(由申请人提供)：种族、家族史和年龄是公认的前列腺癌(PCA)的危险因素，前列腺癌是西方男性最易遗传的癌症之一。雄激素受体(AR)依赖的信号转导通路在前列腺癌的肿瘤生长和进展中起着核心作用。非裔美国人男性前列腺癌的发生率、死亡率和特定阶段的侵袭性高于高加索人。非裔美国人的AR蛋白在良性前列腺组织(高22%)和恶性前列腺组织(高81%)中的表达水平均高于高加索人。到目前为止，AR表达的种族差异仍然是非裔美国人前列腺癌侵袭性增加的少数可能解释之一。因此，AR被认为是PCa的易感基因或易感基因。已有研究表明，在去雄激素治疗前后，在前列腺癌的进展过程中，AR基因的改变会影响AR及其靶基因的表达和活性。AR的分子变化可能导致配体亲和力增强或关闭时间减少，这些变化可能稳定AR并增加AR的表达。如果AR的分子变化在非裔美国人中发生得更频繁，这些变化可能会导致AR蛋白的过度表达，进而导致AR调节基因的过度表达，从而促进前列腺癌的生长。寻找生殖系风险等位基因及其潜在的生物活性一直是旨在解释前列腺癌的遗传基础和不成比例的种族分布的主要研究兴趣。我们在一个高危非裔美国人家庭的四名患者中发现了AR-A1675T DNA结合域(Thr559Ser)的一个新的种系错义突变，该家庭有两代人中的九名受前列腺癌影响的男性。这些数据使我们假设，AR-A1675T突变是一种胚系，具有有利于非裔美国人前列腺癌发生的生物学特征，是一种易感或危险等位基因。这一假设将通过两个具体目标进行检验。在目标1中，我们将确定AR-A1675T突变在非裔美国人中的相对发生率及其与家族性前列腺癌的关系。对AR-A1675T突变的分析将扩大到40个高危非裔美国人和高加索人家庭的400名成员，每个家庭至少包括三名被诊断患有前列腺癌的男性，以及来自这两个种族队列的400名没有被诊断出患有前列腺癌的无关个人。突变将使用等位基因特异的寡核苷酸杂交、基于限制性内切酶的基因分型和基于聚合酶链式反应的自动测序来识别。在目标2中，我们将确定AR-A1675T突变在AR阴性的前列腺癌细胞或永生化的非裔美国人来源的前列腺上皮细胞中的生物学特性。AR-A1675T突变对生长、DNA结合亲和力、转录活性和对雄激素、类固醇激素和非类固醇抗雄激素的反式激活反应的影响将在实验室用常规方法测定。意义：这一探索性项目的结果与未来的大规模研究相结合，包括以非裔美国人为目标的全基因组关联或表达阵列分析，可能会为人群归因风险或预测侵袭性表型的PCa提供更好的检测。 公共卫生相关性：种族和家族史是广泛接受的前列腺癌(PCa)的危险因素。非裔美国人(AA)男性前列腺癌的发病率、死亡率和特定阶段的侵袭性显著高于白人。我们在一个高危AA家系中发现了一个新的种系AR突变，这可能具有预测意义，将为我们提供一种更有效的诊断AAS的方法。

DESCRIPTION (provided by applicant): Race, family history, and age are the unequivocally accepted risk factors for prostate cancer (PCa), as one of the most heritable cancers in western men. Androgen receptor (AR)-dependent signaling has a central role in neoplastic growth and progression of Prostate cancer. The incidence, mortality rate, and stage-specific aggressiveness of PCa in African-American men are higher than Caucasians. African-American men have higher levels of AR protein expression than the Caucasians both in benign (22% higher) and malignant (81% higher) prostate tissue. To date, this racial difference in AR expression remains one of the few possible explanations for the increased aggressiveness of PCa in African Americans. AR has therefore been suggested as a PCa susceptibility or predisposing gene. Genetic alterations in AR have been demonstrated to affect expression and activity of AR and its target genes during the progression of PCa, before or after androgen deprivation therapy. Molecular alterations in AR may allow for enhanced ligand affinity or decreased "off time" and these changes may stabilize AR and increase AR expression. If molecular changes in AR occur more frequently in African Americans, these changes may contribute to AR protein over-expression and, in turn, over-expression of AR-regulated genes that increase PCa growth. The search for germline risk alleles and their potential biological activities have been of major research interests aimed at explaining the hereditary basis and disproportionate racial distribution of PCa. We identified a novel germline missense mutation in the DNA-binding domain of AR-A1675T (Thr559Ser) in four patients of a high-risk African-American family with nine PCa-affected males in two generations. These data led us to hypothesize that the AR-A1675T mutation serves as a germline predisposing or risk allele with biological characteristics that favor prostate carcinogenesis in African-American men. This hypothesis will be tested by two specific aims. In Aim 1, we will determine the relative incidence of the AR-A1675T mutation and its attribution to familial PCa in African Americans. The analysis for the AR-A1675T mutation will be extended to 400 members of 40 high-risk African American and Caucasian families, each containing at least three men diagnosed with PCa and to a pool of 400 unrelated individuals from both ethnic cohorts who have not been diagnosed with PCa. Mutations will be identified using allele-specific oligonucleotide hybridization, restriction enzyme-based genotyping, and PCR- based automated sequencing. In Aim 2, we will determine the biological characteristics of the AR-A1675T mutation in AR-negative PCa cells or immortalized African American-derived prostate epithelial cells. The effect of the AR-A1675T mutation on growth, DNA-binding affinity, transcriptional activity and transactivation response to androgens, steroid hormones, and non-steroidal anti-androgens will be determined using methods routine in the laboratory. Significance: The results of this exploratory project combined with future large-scale studies including African American-targeted genome-wide association or expression array analysis might provide a better detection for population-attributable risk or prediction of the aggressive phenotype of PCa. PUBLIC HEALTH RELEVANCE: Race and family history are the widely accepted risk factors for prostate cancer (PCa). The incidence, mortality rate, and stage-specific aggressiveness of PCa in African-American (AA) men are significantly higher than in Caucasians. Our discovery of a novel germline AR mutation in a high-risk AA family might have predictive significance that would provide us a more effective diagnostic approach in AAs with familial PCa.