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

描述（由申请人提供）：种族、家族史和年龄是前列腺癌（PCa）明确接受的危险因素，前列腺癌是西方男性最具遗传性的癌症之一。雄激素受体（AR）依赖信号在前列腺癌的肿瘤生长和进展中起核心作用。非裔美国男性前列腺癌的发病率、死亡率和分期特异性侵袭性高于白种人。非裔美国男性在良性前列腺组织（高22%）和恶性前列腺组织（高81%）中的AR蛋白表达水平都高于白种人。迄今为止，这种AR表达的种族差异仍然是非洲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的易感性或易感基因。在前列腺癌进展过程中，雄激素剥夺治疗前后，AR的遗传改变已被证明会影响AR及其靶基因的表达和活性。AR的分子改变可能会增强配体亲和力或减少“关闭时间”，这些变化可能会稳定AR并增加AR表达。如果非裔美国人的AR分子变化更频繁，这些变化可能导致AR蛋白过度表达，进而导致AR调节基因过度表达，从而增加前列腺癌的生长。寻找种系风险等位基因及其潜在的生物学活性一直是主要的研究兴趣，旨在解释PCa的遗传基础和不成比例的种族分布。我们在一个高风险的非裔美国家庭的四名患者中发现了AR-A1675T (Thr559Ser) dna结合域的一种新的种系错义突变，该家庭在两代中有9名患pca的男性。这些数据使我们假设AR-A1675T突变是一种种系易感或风险等位基因，具有有利于非裔美国男性前列腺癌发生的生物学特征。这一假设将由两个具体目标来检验。在Aim 1中，我们将确定非裔美国人AR-A1675T突变的相对发生率及其与家族性PCa的关系。对AR-A1675T突变的分析将扩展到40个高风险非裔美国人和高加索人家庭的400名成员，每个家庭至少包含3名被诊断为PCa的男性，以及来自两个种族队列中未被诊断为PCa的400名无血缘关系的个体。突变将被鉴定使用等位基因特异性寡核苷酸杂交，限制性内切酶为基础的基因分型，和PCR为基础的自动测序。在Aim 2中，我们将确定ar阴性PCa细胞或永生的非裔美国人来源的前列腺上皮细胞中AR-A1675T突变的生物学特性。AR-A1675T突变对生长、dna结合亲和力、转录活性和对雄激素、类固醇激素和非甾体抗雄激素的反激活反应的影响将采用实验室常规方法测定。意义：本探索性项目的结果结合未来的大规模研究，包括针对非洲裔美国人的全基因组关联或表达阵列分析，可能为更好地检测人群归因风险或预测PCa的侵袭性表型提供更好的方法。

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.